mirror of
https://github.com/torvalds/linux.git
synced 2024-11-10 06:01:57 +00:00
3efc57369a
* KVM currently invalidates the entirety of the page tables, not just
those for the memslot being touched, when a memslot is moved or deleted.
The former does not have particularly noticeable overhead, but Intel's
TDX will require the guest to re-accept private pages if they are
dropped from the secure EPT, which is a non starter. Actually,
the only reason why this is not already being done is a bug which
was never fully investigated and caused VM instability with assigned
GeForce GPUs, so allow userspace to opt into the new behavior.
* Advertise AVX10.1 to userspace (effectively prep work for the "real" AVX10
functionality that is on the horizon).
* Rework common MSR handling code to suppress errors on userspace accesses to
unsupported-but-advertised MSRs. This will allow removing (almost?) all of
KVM's exemptions for userspace access to MSRs that shouldn't exist based on
the vCPU model (the actual cleanup is non-trivial future work).
* Rework KVM's handling of x2APIC ICR, again, because AMD (x2AVIC) splits the
64-bit value into the legacy ICR and ICR2 storage, whereas Intel (APICv)
stores the entire 64-bit value at the ICR offset.
* Fix a bug where KVM would fail to exit to userspace if one was triggered by
a fastpath exit handler.
* Add fastpath handling of HLT VM-Exit to expedite re-entering the guest when
there's already a pending wake event at the time of the exit.
* Fix a WARN caused by RSM entering a nested guest from SMM with invalid guest
state, by forcing the vCPU out of guest mode prior to signalling SHUTDOWN
(the SHUTDOWN hits the VM altogether, not the nested guest)
* Overhaul the "unprotect and retry" logic to more precisely identify cases
where retrying is actually helpful, and to harden all retry paths against
putting the guest into an infinite retry loop.
* Add support for yielding, e.g. to honor NEED_RESCHED, when zapping rmaps in
the shadow MMU.
* Refactor pieces of the shadow MMU related to aging SPTEs in prepartion for
adding multi generation LRU support in KVM.
* Don't stuff the RSB after VM-Exit when RETPOLINE=y and AutoIBRS is enabled,
i.e. when the CPU has already flushed the RSB.
* Trace the per-CPU host save area as a VMCB pointer to improve readability
and cleanup the retrieval of the SEV-ES host save area.
* Remove unnecessary accounting of temporary nested VMCB related allocations.
* Set FINAL/PAGE in the page fault error code for EPT violations if and only
if the GVA is valid. If the GVA is NOT valid, there is no guest-side page
table walk and so stuffing paging related metadata is nonsensical.
* Fix a bug where KVM would incorrectly synthesize a nested VM-Exit instead of
emulating posted interrupt delivery to L2.
* Add a lockdep assertion to detect unsafe accesses of vmcs12 structures.
* Harden eVMCS loading against an impossible NULL pointer deref (really truly
should be impossible).
* Minor SGX fix and a cleanup.
* Misc cleanups
Generic:
* Register KVM's cpuhp and syscore callbacks when enabling virtualization in
hardware, as the sole purpose of said callbacks is to disable and re-enable
virtualization as needed.
* Enable virtualization when KVM is loaded, not right before the first VM
is created. Together with the previous change, this simplifies a
lot the logic of the callbacks, because their very existence implies
virtualization is enabled.
* Fix a bug that results in KVM prematurely exiting to userspace for coalesced
MMIO/PIO in many cases, clean up the related code, and add a testcase.
* Fix a bug in kvm_clear_guest() where it would trigger a buffer overflow _if_
the gpa+len crosses a page boundary, which thankfully is guaranteed to not
happen in the current code base. Add WARNs in more helpers that read/write
guest memory to detect similar bugs.
Selftests:
* Fix a goof that caused some Hyper-V tests to be skipped when run on bare
metal, i.e. NOT in a VM.
* Add a regression test for KVM's handling of SHUTDOWN for an SEV-ES guest.
* Explicitly include one-off assets in .gitignore. Past Sean was completely
wrong about not being able to detect missing .gitignore entries.
* Verify userspace single-stepping works when KVM happens to handle a VM-Exit
in its fastpath.
* Misc cleanups
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Merge tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm
Pull x86 kvm updates from Paolo Bonzini:
"x86:
- KVM currently invalidates the entirety of the page tables, not just
those for the memslot being touched, when a memslot is moved or
deleted.
This does not traditionally have particularly noticeable overhead,
but Intel's TDX will require the guest to re-accept private pages
if they are dropped from the secure EPT, which is a non starter.
Actually, the only reason why this is not already being done is a
bug which was never fully investigated and caused VM instability
with assigned GeForce GPUs, so allow userspace to opt into the new
behavior.
- Advertise AVX10.1 to userspace (effectively prep work for the
"real" AVX10 functionality that is on the horizon)
- Rework common MSR handling code to suppress errors on userspace
accesses to unsupported-but-advertised MSRs
This will allow removing (almost?) all of KVM's exemptions for
userspace access to MSRs that shouldn't exist based on the vCPU
model (the actual cleanup is non-trivial future work)
- Rework KVM's handling of x2APIC ICR, again, because AMD (x2AVIC)
splits the 64-bit value into the legacy ICR and ICR2 storage,
whereas Intel (APICv) stores the entire 64-bit value at the ICR
offset
- Fix a bug where KVM would fail to exit to userspace if one was
triggered by a fastpath exit handler
- Add fastpath handling of HLT VM-Exit to expedite re-entering the
guest when there's already a pending wake event at the time of the
exit
- Fix a WARN caused by RSM entering a nested guest from SMM with
invalid guest state, by forcing the vCPU out of guest mode prior to
signalling SHUTDOWN (the SHUTDOWN hits the VM altogether, not the
nested guest)
- Overhaul the "unprotect and retry" logic to more precisely identify
cases where retrying is actually helpful, and to harden all retry
paths against putting the guest into an infinite retry loop
- Add support for yielding, e.g. to honor NEED_RESCHED, when zapping
rmaps in the shadow MMU
- Refactor pieces of the shadow MMU related to aging SPTEs in
prepartion for adding multi generation LRU support in KVM
- Don't stuff the RSB after VM-Exit when RETPOLINE=y and AutoIBRS is
enabled, i.e. when the CPU has already flushed the RSB
- Trace the per-CPU host save area as a VMCB pointer to improve
readability and cleanup the retrieval of the SEV-ES host save area
- Remove unnecessary accounting of temporary nested VMCB related
allocations
- Set FINAL/PAGE in the page fault error code for EPT violations if
and only if the GVA is valid. If the GVA is NOT valid, there is no
guest-side page table walk and so stuffing paging related metadata
is nonsensical
- Fix a bug where KVM would incorrectly synthesize a nested VM-Exit
instead of emulating posted interrupt delivery to L2
- Add a lockdep assertion to detect unsafe accesses of vmcs12
structures
- Harden eVMCS loading against an impossible NULL pointer deref
(really truly should be impossible)
- Minor SGX fix and a cleanup
- Misc cleanups
Generic:
- Register KVM's cpuhp and syscore callbacks when enabling
virtualization in hardware, as the sole purpose of said callbacks
is to disable and re-enable virtualization as needed
- Enable virtualization when KVM is loaded, not right before the
first VM is created
Together with the previous change, this simplifies a lot the logic
of the callbacks, because their very existence implies
virtualization is enabled
- Fix a bug that results in KVM prematurely exiting to userspace for
coalesced MMIO/PIO in many cases, clean up the related code, and
add a testcase
- Fix a bug in kvm_clear_guest() where it would trigger a buffer
overflow _if_ the gpa+len crosses a page boundary, which thankfully
is guaranteed to not happen in the current code base. Add WARNs in
more helpers that read/write guest memory to detect similar bugs
Selftests:
- Fix a goof that caused some Hyper-V tests to be skipped when run on
bare metal, i.e. NOT in a VM
- Add a regression test for KVM's handling of SHUTDOWN for an SEV-ES
guest
- Explicitly include one-off assets in .gitignore. Past Sean was
completely wrong about not being able to detect missing .gitignore
entries
- Verify userspace single-stepping works when KVM happens to handle a
VM-Exit in its fastpath
- Misc cleanups"
* tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm: (127 commits)
Documentation: KVM: fix warning in "make htmldocs"
s390: Enable KVM_S390_UCONTROL config in debug_defconfig
selftests: kvm: s390: Add VM run test case
KVM: SVM: let alternatives handle the cases when RSB filling is required
KVM: VMX: Set PFERR_GUEST_{FINAL,PAGE}_MASK if and only if the GVA is valid
KVM: x86/mmu: Use KVM_PAGES_PER_HPAGE() instead of an open coded equivalent
KVM: x86/mmu: Add KVM_RMAP_MANY to replace open coded '1' and '1ul' literals
KVM: x86/mmu: Fold mmu_spte_age() into kvm_rmap_age_gfn_range()
KVM: x86/mmu: Morph kvm_handle_gfn_range() into an aging specific helper
KVM: x86/mmu: Honor NEED_RESCHED when zapping rmaps and blocking is allowed
KVM: x86/mmu: Add a helper to walk and zap rmaps for a memslot
KVM: x86/mmu: Plumb a @can_yield parameter into __walk_slot_rmaps()
KVM: x86/mmu: Move walk_slot_rmaps() up near for_each_slot_rmap_range()
KVM: x86/mmu: WARN on MMIO cache hit when emulating write-protected gfn
KVM: x86/mmu: Detect if unprotect will do anything based on invalid_list
KVM: x86/mmu: Subsume kvm_mmu_unprotect_page() into the and_retry() version
KVM: x86: Rename reexecute_instruction()=>kvm_unprotect_and_retry_on_failure()
KVM: x86: Update retry protection fields when forcing retry on emulation failure
KVM: x86: Apply retry protection to "unprotect on failure" path
KVM: x86: Check EMULTYPE_WRITE_PF_TO_SP before unprotecting gfn
...
7680 lines
275 KiB
Plaintext
7680 lines
275 KiB
Plaintext
accept_memory= [MM]
|
||
Format: { eager | lazy }
|
||
default: lazy
|
||
By default, unaccepted memory is accepted lazily to
|
||
avoid prolonged boot times. The lazy option will add
|
||
some runtime overhead until all memory is eventually
|
||
accepted. In most cases the overhead is negligible.
|
||
For some workloads or for debugging purposes
|
||
accept_memory=eager can be used to accept all memory
|
||
at once during boot.
|
||
|
||
acpi= [HW,ACPI,X86,ARM64,RISCV64,EARLY]
|
||
Advanced Configuration and Power Interface
|
||
Format: { force | on | off | strict | noirq | rsdt |
|
||
copy_dsdt | nospcr }
|
||
force -- enable ACPI if default was off
|
||
on -- enable ACPI but allow fallback to DT [arm64,riscv64]
|
||
off -- disable ACPI if default was on
|
||
noirq -- do not use ACPI for IRQ routing
|
||
strict -- Be less tolerant of platforms that are not
|
||
strictly ACPI specification compliant.
|
||
rsdt -- prefer RSDT over (default) XSDT
|
||
copy_dsdt -- copy DSDT to memory
|
||
nospcr -- disable console in ACPI SPCR table as
|
||
default _serial_ console on ARM64
|
||
For ARM64, ONLY "acpi=off", "acpi=on", "acpi=force" or
|
||
"acpi=nospcr" are available
|
||
For RISCV64, ONLY "acpi=off", "acpi=on" or "acpi=force"
|
||
are available
|
||
|
||
See also Documentation/power/runtime_pm.rst, pci=noacpi
|
||
|
||
acpi_apic_instance= [ACPI,IOAPIC,EARLY]
|
||
Format: <int>
|
||
2: use 2nd APIC table, if available
|
||
1,0: use 1st APIC table
|
||
default: 0
|
||
|
||
acpi_backlight= [HW,ACPI]
|
||
{ vendor | video | native | none }
|
||
If set to vendor, prefer vendor-specific driver
|
||
(e.g. thinkpad_acpi, sony_acpi, etc.) instead
|
||
of the ACPI video.ko driver.
|
||
If set to video, use the ACPI video.ko driver.
|
||
If set to native, use the device's native backlight mode.
|
||
If set to none, disable the ACPI backlight interface.
|
||
|
||
acpi_force_32bit_fadt_addr [ACPI,EARLY]
|
||
force FADT to use 32 bit addresses rather than the
|
||
64 bit X_* addresses. Some firmware have broken 64
|
||
bit addresses for force ACPI ignore these and use
|
||
the older legacy 32 bit addresses.
|
||
|
||
acpica_no_return_repair [HW, ACPI]
|
||
Disable AML predefined validation mechanism
|
||
This mechanism can repair the evaluation result to make
|
||
the return objects more ACPI specification compliant.
|
||
This option is useful for developers to identify the
|
||
root cause of an AML interpreter issue when the issue
|
||
has something to do with the repair mechanism.
|
||
|
||
acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
|
||
acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
|
||
Format: <int>
|
||
CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
|
||
debug output. Bits in debug_layer correspond to a
|
||
_COMPONENT in an ACPI source file, e.g.,
|
||
#define _COMPONENT ACPI_EVENTS
|
||
Bits in debug_level correspond to a level in
|
||
ACPI_DEBUG_PRINT statements, e.g.,
|
||
ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
|
||
The debug_level mask defaults to "info". See
|
||
Documentation/firmware-guide/acpi/debug.rst for more information about
|
||
debug layers and levels.
|
||
|
||
Enable processor driver info messages:
|
||
acpi.debug_layer=0x20000000
|
||
Enable AML "Debug" output, i.e., stores to the Debug
|
||
object while interpreting AML:
|
||
acpi.debug_layer=0xffffffff acpi.debug_level=0x2
|
||
Enable all messages related to ACPI hardware:
|
||
acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
|
||
|
||
Some values produce so much output that the system is
|
||
unusable. The "log_buf_len" parameter may be useful
|
||
if you need to capture more output.
|
||
|
||
acpi_enforce_resources= [ACPI]
|
||
{ strict | lax | no }
|
||
Check for resource conflicts between native drivers
|
||
and ACPI OperationRegions (SystemIO and SystemMemory
|
||
only). IO ports and memory declared in ACPI might be
|
||
used by the ACPI subsystem in arbitrary AML code and
|
||
can interfere with legacy drivers.
|
||
strict (default): access to resources claimed by ACPI
|
||
is denied; legacy drivers trying to access reserved
|
||
resources will fail to bind to device using them.
|
||
lax: access to resources claimed by ACPI is allowed;
|
||
legacy drivers trying to access reserved resources
|
||
will bind successfully but a warning message is logged.
|
||
no: ACPI OperationRegions are not marked as reserved,
|
||
no further checks are performed.
|
||
|
||
acpi_force_table_verification [HW,ACPI,EARLY]
|
||
Enable table checksum verification during early stage.
|
||
By default, this is disabled due to x86 early mapping
|
||
size limitation.
|
||
|
||
acpi_irq_balance [HW,ACPI]
|
||
ACPI will balance active IRQs
|
||
default in APIC mode
|
||
|
||
acpi_irq_nobalance [HW,ACPI]
|
||
ACPI will not move active IRQs (default)
|
||
default in PIC mode
|
||
|
||
acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
|
||
Format: <irq>,<irq>...
|
||
|
||
acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
|
||
use by PCI
|
||
Format: <irq>,<irq>...
|
||
|
||
acpi_mask_gpe= [HW,ACPI]
|
||
Due to the existence of _Lxx/_Exx, some GPEs triggered
|
||
by unsupported hardware/firmware features can result in
|
||
GPE floodings that cannot be automatically disabled by
|
||
the GPE dispatcher.
|
||
This facility can be used to prevent such uncontrolled
|
||
GPE floodings.
|
||
Format: <byte> or <bitmap-list>
|
||
|
||
acpi_no_auto_serialize [HW,ACPI]
|
||
Disable auto-serialization of AML methods
|
||
AML control methods that contain the opcodes to create
|
||
named objects will be marked as "Serialized" by the
|
||
auto-serialization feature.
|
||
This feature is enabled by default.
|
||
This option allows to turn off the feature.
|
||
|
||
acpi_no_memhotplug [ACPI] Disable memory hotplug. Useful for kdump
|
||
kernels.
|
||
|
||
acpi_no_static_ssdt [HW,ACPI,EARLY]
|
||
Disable installation of static SSDTs at early boot time
|
||
By default, SSDTs contained in the RSDT/XSDT will be
|
||
installed automatically and they will appear under
|
||
/sys/firmware/acpi/tables.
|
||
This option turns off this feature.
|
||
Note that specifying this option does not affect
|
||
dynamic table installation which will install SSDT
|
||
tables to /sys/firmware/acpi/tables/dynamic.
|
||
|
||
acpi_no_watchdog [HW,ACPI,WDT]
|
||
Ignore the ACPI-based watchdog interface (WDAT) and let
|
||
a native driver control the watchdog device instead.
|
||
|
||
acpi_rsdp= [ACPI,EFI,KEXEC,EARLY]
|
||
Pass the RSDP address to the kernel, mostly used
|
||
on machines running EFI runtime service to boot the
|
||
second kernel for kdump.
|
||
|
||
acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
|
||
Format: To spoof as Windows 98: ="Microsoft Windows"
|
||
|
||
acpi_rev_override [ACPI] Override the _REV object to return 5 (instead
|
||
of 2 which is mandated by ACPI 6) as the supported ACPI
|
||
specification revision (when using this switch, it may
|
||
be necessary to carry out a cold reboot _twice_ in a
|
||
row to make it take effect on the platform firmware).
|
||
|
||
acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
|
||
acpi_osi="string1" # add string1
|
||
acpi_osi="!string2" # remove string2
|
||
acpi_osi=!* # remove all strings
|
||
acpi_osi=! # disable all built-in OS vendor
|
||
strings
|
||
acpi_osi=!! # enable all built-in OS vendor
|
||
strings
|
||
acpi_osi= # disable all strings
|
||
|
||
'acpi_osi=!' can be used in combination with single or
|
||
multiple 'acpi_osi="string1"' to support specific OS
|
||
vendor string(s). Note that such command can only
|
||
affect the default state of the OS vendor strings, thus
|
||
it cannot affect the default state of the feature group
|
||
strings and the current state of the OS vendor strings,
|
||
specifying it multiple times through kernel command line
|
||
is meaningless. This command is useful when one do not
|
||
care about the state of the feature group strings which
|
||
should be controlled by the OSPM.
|
||
Examples:
|
||
1. 'acpi_osi=! acpi_osi="Windows 2000"' is equivalent
|
||
to 'acpi_osi="Windows 2000" acpi_osi=!', they all
|
||
can make '_OSI("Windows 2000")' TRUE.
|
||
|
||
'acpi_osi=' cannot be used in combination with other
|
||
'acpi_osi=' command lines, the _OSI method will not
|
||
exist in the ACPI namespace. NOTE that such command can
|
||
only affect the _OSI support state, thus specifying it
|
||
multiple times through kernel command line is also
|
||
meaningless.
|
||
Examples:
|
||
1. 'acpi_osi=' can make 'CondRefOf(_OSI, Local1)'
|
||
FALSE.
|
||
|
||
'acpi_osi=!*' can be used in combination with single or
|
||
multiple 'acpi_osi="string1"' to support specific
|
||
string(s). Note that such command can affect the
|
||
current state of both the OS vendor strings and the
|
||
feature group strings, thus specifying it multiple times
|
||
through kernel command line is meaningful. But it may
|
||
still not able to affect the final state of a string if
|
||
there are quirks related to this string. This command
|
||
is useful when one want to control the state of the
|
||
feature group strings to debug BIOS issues related to
|
||
the OSPM features.
|
||
Examples:
|
||
1. 'acpi_osi="Module Device" acpi_osi=!*' can make
|
||
'_OSI("Module Device")' FALSE.
|
||
2. 'acpi_osi=!* acpi_osi="Module Device"' can make
|
||
'_OSI("Module Device")' TRUE.
|
||
3. 'acpi_osi=! acpi_osi=!* acpi_osi="Windows 2000"' is
|
||
equivalent to
|
||
'acpi_osi=!* acpi_osi=! acpi_osi="Windows 2000"'
|
||
and
|
||
'acpi_osi=!* acpi_osi="Windows 2000" acpi_osi=!',
|
||
they all will make '_OSI("Windows 2000")' TRUE.
|
||
|
||
acpi_pm_good [X86]
|
||
Override the pmtimer bug detection: force the kernel
|
||
to assume that this machine's pmtimer latches its value
|
||
and always returns good values.
|
||
|
||
acpi_sci= [HW,ACPI,EARLY] ACPI System Control Interrupt trigger mode
|
||
Format: { level | edge | high | low }
|
||
|
||
acpi_skip_timer_override [HW,ACPI,EARLY]
|
||
Recognize and ignore IRQ0/pin2 Interrupt Override.
|
||
For broken nForce2 BIOS resulting in XT-PIC timer.
|
||
|
||
acpi_sleep= [HW,ACPI] Sleep options
|
||
Format: { s3_bios, s3_mode, s3_beep, s4_hwsig,
|
||
s4_nohwsig, old_ordering, nonvs,
|
||
sci_force_enable, nobl }
|
||
See Documentation/power/video.rst for information on
|
||
s3_bios and s3_mode.
|
||
s3_beep is for debugging; it makes the PC's speaker beep
|
||
as soon as the kernel's real-mode entry point is called.
|
||
s4_hwsig causes the kernel to check the ACPI hardware
|
||
signature during resume from hibernation, and gracefully
|
||
refuse to resume if it has changed. This complies with
|
||
the ACPI specification but not with reality, since
|
||
Windows does not do this and many laptops do change it
|
||
on docking. So the default behaviour is to allow resume
|
||
and simply warn when the signature changes, unless the
|
||
s4_hwsig option is enabled.
|
||
s4_nohwsig prevents ACPI hardware signature from being
|
||
used (or even warned about) during resume.
|
||
old_ordering causes the ACPI 1.0 ordering of the _PTS
|
||
control method, with respect to putting devices into
|
||
low power states, to be enforced (the ACPI 2.0 ordering
|
||
of _PTS is used by default).
|
||
nonvs prevents the kernel from saving/restoring the
|
||
ACPI NVS memory during suspend/hibernation and resume.
|
||
sci_force_enable causes the kernel to set SCI_EN directly
|
||
on resume from S1/S3 (which is against the ACPI spec,
|
||
but some broken systems don't work without it).
|
||
nobl causes the internal blacklist of systems known to
|
||
behave incorrectly in some ways with respect to system
|
||
suspend and resume to be ignored (use wisely).
|
||
|
||
acpi_use_timer_override [HW,ACPI,EARLY]
|
||
Use timer override. For some broken Nvidia NF5 boards
|
||
that require a timer override, but don't have HPET
|
||
|
||
add_efi_memmap [EFI,X86,EARLY] Include EFI memory map in
|
||
kernel's map of available physical RAM.
|
||
|
||
agp= [AGP]
|
||
{ off | try_unsupported }
|
||
off: disable AGP support
|
||
try_unsupported: try to drive unsupported chipsets
|
||
(may crash computer or cause data corruption)
|
||
|
||
ALSA [HW,ALSA]
|
||
See Documentation/sound/alsa-configuration.rst
|
||
|
||
alignment= [KNL,ARM]
|
||
Allow the default userspace alignment fault handler
|
||
behaviour to be specified. Bit 0 enables warnings,
|
||
bit 1 enables fixups, and bit 2 sends a segfault.
|
||
|
||
align_va_addr= [X86-64]
|
||
Align virtual addresses by clearing slice [14:12] when
|
||
allocating a VMA at process creation time. This option
|
||
gives you up to 3% performance improvement on AMD F15h
|
||
machines (where it is enabled by default) for a
|
||
CPU-intensive style benchmark, and it can vary highly in
|
||
a microbenchmark depending on workload and compiler.
|
||
|
||
32: only for 32-bit processes
|
||
64: only for 64-bit processes
|
||
on: enable for both 32- and 64-bit processes
|
||
off: disable for both 32- and 64-bit processes
|
||
|
||
alloc_snapshot [FTRACE]
|
||
Allocate the ftrace snapshot buffer on boot up when the
|
||
main buffer is allocated. This is handy if debugging
|
||
and you need to use tracing_snapshot() on boot up, and
|
||
do not want to use tracing_snapshot_alloc() as it needs
|
||
to be done where GFP_KERNEL allocations are allowed.
|
||
|
||
allow_mismatched_32bit_el0 [ARM64,EARLY]
|
||
Allow execve() of 32-bit applications and setting of the
|
||
PER_LINUX32 personality on systems where only a strict
|
||
subset of the CPUs support 32-bit EL0. When this
|
||
parameter is present, the set of CPUs supporting 32-bit
|
||
EL0 is indicated by /sys/devices/system/cpu/aarch32_el0
|
||
and hot-unplug operations may be restricted.
|
||
|
||
See Documentation/arch/arm64/asymmetric-32bit.rst for more
|
||
information.
|
||
|
||
amd_iommu= [HW,X86-64]
|
||
Pass parameters to the AMD IOMMU driver in the system.
|
||
Possible values are:
|
||
fullflush - Deprecated, equivalent to iommu.strict=1
|
||
off - do not initialize any AMD IOMMU found in
|
||
the system
|
||
force_isolation - Force device isolation for all
|
||
devices. The IOMMU driver is not
|
||
allowed anymore to lift isolation
|
||
requirements as needed. This option
|
||
does not override iommu=pt
|
||
force_enable - Force enable the IOMMU on platforms known
|
||
to be buggy with IOMMU enabled. Use this
|
||
option with care.
|
||
pgtbl_v1 - Use v1 page table for DMA-API (Default).
|
||
pgtbl_v2 - Use v2 page table for DMA-API.
|
||
irtcachedis - Disable Interrupt Remapping Table (IRT) caching.
|
||
nohugepages - Limit page-sizes used for v1 page-tables
|
||
to 4 KiB.
|
||
v2_pgsizes_only - Limit page-sizes used for v1 page-tables
|
||
to 4KiB/2Mib/1GiB.
|
||
|
||
|
||
amd_iommu_dump= [HW,X86-64]
|
||
Enable AMD IOMMU driver option to dump the ACPI table
|
||
for AMD IOMMU. With this option enabled, AMD IOMMU
|
||
driver will print ACPI tables for AMD IOMMU during
|
||
IOMMU initialization.
|
||
|
||
amd_iommu_intr= [HW,X86-64]
|
||
Specifies one of the following AMD IOMMU interrupt
|
||
remapping modes:
|
||
legacy - Use legacy interrupt remapping mode.
|
||
vapic - Use virtual APIC mode, which allows IOMMU
|
||
to inject interrupts directly into guest.
|
||
This mode requires kvm-amd.avic=1.
|
||
(Default when IOMMU HW support is present.)
|
||
|
||
amd_pstate= [X86,EARLY]
|
||
disable
|
||
Do not enable amd_pstate as the default
|
||
scaling driver for the supported processors
|
||
passive
|
||
Use amd_pstate with passive mode as a scaling driver.
|
||
In this mode autonomous selection is disabled.
|
||
Driver requests a desired performance level and platform
|
||
tries to match the same performance level if it is
|
||
satisfied by guaranteed performance level.
|
||
active
|
||
Use amd_pstate_epp driver instance as the scaling driver,
|
||
driver provides a hint to the hardware if software wants
|
||
to bias toward performance (0x0) or energy efficiency (0xff)
|
||
to the CPPC firmware. then CPPC power algorithm will
|
||
calculate the runtime workload and adjust the realtime cores
|
||
frequency.
|
||
guided
|
||
Activate guided autonomous mode. Driver requests minimum and
|
||
maximum performance level and the platform autonomously
|
||
selects a performance level in this range and appropriate
|
||
to the current workload.
|
||
|
||
amd_prefcore=
|
||
[X86]
|
||
disable
|
||
Disable amd-pstate preferred core.
|
||
|
||
amijoy.map= [HW,JOY] Amiga joystick support
|
||
Map of devices attached to JOY0DAT and JOY1DAT
|
||
Format: <a>,<b>
|
||
See also Documentation/input/joydev/joystick.rst
|
||
|
||
analog.map= [HW,JOY] Analog joystick and gamepad support
|
||
Specifies type or capabilities of an analog joystick
|
||
connected to one of 16 gameports
|
||
Format: <type1>,<type2>,..<type16>
|
||
|
||
apc= [HW,SPARC]
|
||
Power management functions (SPARCstation-4/5 + deriv.)
|
||
Format: noidle
|
||
Disable APC CPU standby support. SPARCstation-Fox does
|
||
not play well with APC CPU idle - disable it if you have
|
||
APC and your system crashes randomly.
|
||
|
||
apic= [APIC,X86,EARLY] Advanced Programmable Interrupt Controller
|
||
Change the output verbosity while booting
|
||
Format: { quiet (default) | verbose | debug }
|
||
Change the amount of debugging information output
|
||
when initialising the APIC and IO-APIC components.
|
||
For X86-32, this can also be used to specify an APIC
|
||
driver name.
|
||
Format: apic=driver_name
|
||
Examples: apic=bigsmp
|
||
|
||
apic_extnmi= [APIC,X86,EARLY] External NMI delivery setting
|
||
Format: { bsp (default) | all | none }
|
||
bsp: External NMI is delivered only to CPU 0
|
||
all: External NMIs are broadcast to all CPUs as a
|
||
backup of CPU 0
|
||
none: External NMI is masked for all CPUs. This is
|
||
useful so that a dump capture kernel won't be
|
||
shot down by NMI
|
||
|
||
autoconf= [IPV6]
|
||
See Documentation/networking/ipv6.rst.
|
||
|
||
apm= [APM] Advanced Power Management
|
||
See header of arch/x86/kernel/apm_32.c.
|
||
|
||
apparmor= [APPARMOR] Disable or enable AppArmor at boot time
|
||
Format: { "0" | "1" }
|
||
See security/apparmor/Kconfig help text
|
||
0 -- disable.
|
||
1 -- enable.
|
||
Default value is set via kernel config option.
|
||
|
||
arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
|
||
Format: <io>,<irq>,<nodeID>
|
||
|
||
arm64.no32bit_el0 [ARM64] Unconditionally disable the execution of
|
||
32 bit applications.
|
||
|
||
arm64.nobti [ARM64] Unconditionally disable Branch Target
|
||
Identification support
|
||
|
||
arm64.nomops [ARM64] Unconditionally disable Memory Copy and Memory
|
||
Set instructions support
|
||
|
||
arm64.nomte [ARM64] Unconditionally disable Memory Tagging Extension
|
||
support
|
||
|
||
arm64.nopauth [ARM64] Unconditionally disable Pointer Authentication
|
||
support
|
||
|
||
arm64.nosme [ARM64] Unconditionally disable Scalable Matrix
|
||
Extension support
|
||
|
||
arm64.nosve [ARM64] Unconditionally disable Scalable Vector
|
||
Extension support
|
||
|
||
ataflop= [HW,M68k]
|
||
|
||
atarimouse= [HW,MOUSE] Atari Mouse
|
||
|
||
atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
|
||
EzKey and similar keyboards
|
||
|
||
atkbd.reset= [HW] Reset keyboard during initialization
|
||
|
||
atkbd.set= [HW] Select keyboard code set
|
||
Format: <int> (2 = AT (default), 3 = PS/2)
|
||
|
||
atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
|
||
keyboards
|
||
|
||
atkbd.softraw= [HW] Choose between synthetic and real raw mode
|
||
Format: <bool> (0 = real, 1 = synthetic (default))
|
||
|
||
atkbd.softrepeat= [HW]
|
||
Use software keyboard repeat
|
||
|
||
audit= [KNL] Enable the audit sub-system
|
||
Format: { "0" | "1" | "off" | "on" }
|
||
0 | off - kernel audit is disabled and can not be
|
||
enabled until the next reboot
|
||
unset - kernel audit is initialized but disabled and
|
||
will be fully enabled by the userspace auditd.
|
||
1 | on - kernel audit is initialized and partially
|
||
enabled, storing at most audit_backlog_limit
|
||
messages in RAM until it is fully enabled by the
|
||
userspace auditd.
|
||
Default: unset
|
||
|
||
audit_backlog_limit= [KNL] Set the audit queue size limit.
|
||
Format: <int> (must be >=0)
|
||
Default: 64
|
||
|
||
bau= [X86_UV] Enable the BAU on SGI UV. The default
|
||
behavior is to disable the BAU (i.e. bau=0).
|
||
Format: { "0" | "1" }
|
||
0 - Disable the BAU.
|
||
1 - Enable the BAU.
|
||
unset - Disable the BAU.
|
||
|
||
baycom_epp= [HW,AX25]
|
||
Format: <io>,<mode>
|
||
|
||
baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
|
||
Format: <io>,<mode>
|
||
See header of drivers/net/hamradio/baycom_par.c.
|
||
|
||
baycom_ser_fdx= [HW,AX25]
|
||
BayCom Serial Port AX.25 Modem (Full Duplex Mode)
|
||
Format: <io>,<irq>,<mode>[,<baud>]
|
||
See header of drivers/net/hamradio/baycom_ser_fdx.c.
|
||
|
||
baycom_ser_hdx= [HW,AX25]
|
||
BayCom Serial Port AX.25 Modem (Half Duplex Mode)
|
||
Format: <io>,<irq>,<mode>
|
||
See header of drivers/net/hamradio/baycom_ser_hdx.c.
|
||
|
||
bdev_allow_write_mounted=
|
||
Format: <bool>
|
||
Control the ability to open a mounted block device
|
||
for writing, i.e., allow / disallow writes that bypass
|
||
the FS. This was implemented as a means to prevent
|
||
fuzzers from crashing the kernel by overwriting the
|
||
metadata underneath a mounted FS without its awareness.
|
||
This also prevents destructive formatting of mounted
|
||
filesystems by naive storage tooling that don't use
|
||
O_EXCL. Default is Y and can be changed through the
|
||
Kconfig option CONFIG_BLK_DEV_WRITE_MOUNTED.
|
||
|
||
bert_disable [ACPI]
|
||
Disable BERT OS support on buggy BIOSes.
|
||
|
||
bgrt_disable [ACPI,X86,EARLY]
|
||
Disable BGRT to avoid flickering OEM logo.
|
||
|
||
blkdevparts= Manual partition parsing of block device(s) for
|
||
embedded devices based on command line input.
|
||
See Documentation/block/cmdline-partition.rst
|
||
|
||
boot_delay= [KNL,EARLY]
|
||
Milliseconds to delay each printk during boot.
|
||
Only works if CONFIG_BOOT_PRINTK_DELAY is enabled,
|
||
and you may also have to specify "lpj=". Boot_delay
|
||
values larger than 10 seconds (10000) are assumed
|
||
erroneous and ignored.
|
||
Format: integer
|
||
|
||
bootconfig [KNL,EARLY]
|
||
Extended command line options can be added to an initrd
|
||
and this will cause the kernel to look for it.
|
||
|
||
See Documentation/admin-guide/bootconfig.rst
|
||
|
||
bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
|
||
bttv.radio= Most important insmod options are available as
|
||
kernel args too.
|
||
bttv.pll= See Documentation/admin-guide/media/bttv.rst
|
||
bttv.tuner=
|
||
|
||
bulk_remove=off [PPC] This parameter disables the use of the pSeries
|
||
firmware feature for flushing multiple hpte entries
|
||
at a time.
|
||
|
||
c101= [NET] Moxa C101 synchronous serial card
|
||
|
||
cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
|
||
Sometimes CPU hardware bugs make them report the cache
|
||
size incorrectly. The kernel will attempt work arounds
|
||
to fix known problems, but for some CPUs it is not
|
||
possible to determine what the correct size should be.
|
||
This option provides an override for these situations.
|
||
|
||
carrier_timeout=
|
||
[NET] Specifies amount of time (in seconds) that
|
||
the kernel should wait for a network carrier. By default
|
||
it waits 120 seconds.
|
||
|
||
ca_keys= [KEYS] This parameter identifies a specific key(s) on
|
||
the system trusted keyring to be used for certificate
|
||
trust validation.
|
||
format: { id:<keyid> | builtin }
|
||
|
||
cca= [MIPS,EARLY] Override the kernel pages' cache coherency
|
||
algorithm. Accepted values range from 0 to 7
|
||
inclusive. See arch/mips/include/asm/pgtable-bits.h
|
||
for platform specific values (SB1, Loongson3 and
|
||
others).
|
||
|
||
ccw_timeout_log [S390]
|
||
See Documentation/arch/s390/common_io.rst for details.
|
||
|
||
cgroup_disable= [KNL] Disable a particular controller or optional feature
|
||
Format: {name of the controller(s) or feature(s) to disable}
|
||
The effects of cgroup_disable=foo are:
|
||
- foo isn't auto-mounted if you mount all cgroups in
|
||
a single hierarchy
|
||
- foo isn't visible as an individually mountable
|
||
subsystem
|
||
- if foo is an optional feature then the feature is
|
||
disabled and corresponding cgroup files are not
|
||
created
|
||
{Currently only "memory" controller deal with this and
|
||
cut the overhead, others just disable the usage. So
|
||
only cgroup_disable=memory is actually worthy}
|
||
Specifying "pressure" disables per-cgroup pressure
|
||
stall information accounting feature
|
||
|
||
cgroup_no_v1= [KNL] Disable cgroup controllers and named hierarchies in v1
|
||
Format: { { controller | "all" | "named" }
|
||
[,{ controller | "all" | "named" }...] }
|
||
Like cgroup_disable, but only applies to cgroup v1;
|
||
the blacklisted controllers remain available in cgroup2.
|
||
"all" blacklists all controllers and "named" disables
|
||
named mounts. Specifying both "all" and "named" disables
|
||
all v1 hierarchies.
|
||
|
||
cgroup_favordynmods= [KNL] Enable or Disable favordynmods.
|
||
Format: { "true" | "false" }
|
||
Defaults to the value of CONFIG_CGROUP_FAVOR_DYNMODS.
|
||
|
||
cgroup.memory= [KNL] Pass options to the cgroup memory controller.
|
||
Format: <string>
|
||
nosocket -- Disable socket memory accounting.
|
||
nokmem -- Disable kernel memory accounting.
|
||
nobpf -- Disable BPF memory accounting.
|
||
|
||
checkreqprot= [SELINUX] Set initial checkreqprot flag value.
|
||
Format: { "0" | "1" }
|
||
See security/selinux/Kconfig help text.
|
||
0 -- check protection applied by kernel (includes
|
||
any implied execute protection).
|
||
1 -- check protection requested by application.
|
||
Default value is set via a kernel config option.
|
||
Value can be changed at runtime via
|
||
/sys/fs/selinux/checkreqprot.
|
||
Setting checkreqprot to 1 is deprecated.
|
||
|
||
cio_ignore= [S390]
|
||
See Documentation/arch/s390/common_io.rst for details.
|
||
|
||
clearcpuid=X[,X...] [X86]
|
||
Disable CPUID feature X for the kernel. See
|
||
arch/x86/include/asm/cpufeatures.h for the valid bit
|
||
numbers X. Note the Linux-specific bits are not necessarily
|
||
stable over kernel options, but the vendor-specific
|
||
ones should be.
|
||
X can also be a string as appearing in the flags: line
|
||
in /proc/cpuinfo which does not have the above
|
||
instability issue. However, not all features have names
|
||
in /proc/cpuinfo.
|
||
Note that using this option will taint your kernel.
|
||
Also note that user programs calling CPUID directly
|
||
or using the feature without checking anything
|
||
will still see it. This just prevents it from
|
||
being used by the kernel or shown in /proc/cpuinfo.
|
||
Also note the kernel might malfunction if you disable
|
||
some critical bits.
|
||
|
||
clk_ignore_unused
|
||
[CLK]
|
||
Prevents the clock framework from automatically gating
|
||
clocks that have not been explicitly enabled by a Linux
|
||
device driver but are enabled in hardware at reset or
|
||
by the bootloader/firmware. Note that this does not
|
||
force such clocks to be always-on nor does it reserve
|
||
those clocks in any way. This parameter is useful for
|
||
debug and development, but should not be needed on a
|
||
platform with proper driver support. For more
|
||
information, see Documentation/driver-api/clk.rst.
|
||
|
||
clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
|
||
[Deprecated]
|
||
Forces specified clocksource (if available) to be used
|
||
when calculating gettimeofday(). If specified
|
||
clocksource is not available, it defaults to PIT.
|
||
Format: { pit | tsc | cyclone | pmtmr }
|
||
|
||
clocksource= Override the default clocksource
|
||
Format: <string>
|
||
Override the default clocksource and use the clocksource
|
||
with the name specified.
|
||
Some clocksource names to choose from, depending on
|
||
the platform:
|
||
[all] jiffies (this is the base, fallback clocksource)
|
||
[ACPI] acpi_pm
|
||
[ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
|
||
pxa_timer,timer3,32k_counter,timer0_1
|
||
[X86-32] pit,hpet,tsc;
|
||
scx200_hrt on Geode; cyclone on IBM x440
|
||
[MIPS] MIPS
|
||
[PARISC] cr16
|
||
[S390] tod
|
||
[SH] SuperH
|
||
[SPARC64] tick
|
||
[X86-64] hpet,tsc
|
||
|
||
clocksource.arm_arch_timer.evtstrm=
|
||
[ARM,ARM64,EARLY]
|
||
Format: <bool>
|
||
Enable/disable the eventstream feature of the ARM
|
||
architected timer so that code using WFE-based polling
|
||
loops can be debugged more effectively on production
|
||
systems.
|
||
|
||
clocksource.verify_n_cpus= [KNL]
|
||
Limit the number of CPUs checked for clocksources
|
||
marked with CLOCK_SOURCE_VERIFY_PERCPU that
|
||
are marked unstable due to excessive skew.
|
||
A negative value says to check all CPUs, while
|
||
zero says not to check any. Values larger than
|
||
nr_cpu_ids are silently truncated to nr_cpu_ids.
|
||
The actual CPUs are chosen randomly, with
|
||
no replacement if the same CPU is chosen twice.
|
||
|
||
clocksource-wdtest.holdoff= [KNL]
|
||
Set the time in seconds that the clocksource
|
||
watchdog test waits before commencing its tests.
|
||
Defaults to zero when built as a module and to
|
||
10 seconds when built into the kernel.
|
||
|
||
cma=nn[MG]@[start[MG][-end[MG]]]
|
||
[KNL,CMA,EARLY]
|
||
Sets the size of kernel global memory area for
|
||
contiguous memory allocations and optionally the
|
||
placement constraint by the physical address range of
|
||
memory allocations. A value of 0 disables CMA
|
||
altogether. For more information, see
|
||
kernel/dma/contiguous.c
|
||
|
||
cma_pernuma=nn[MG]
|
||
[KNL,CMA,EARLY]
|
||
Sets the size of kernel per-numa memory area for
|
||
contiguous memory allocations. A value of 0 disables
|
||
per-numa CMA altogether. And If this option is not
|
||
specified, the default value is 0.
|
||
With per-numa CMA enabled, DMA users on node nid will
|
||
first try to allocate buffer from the pernuma area
|
||
which is located in node nid, if the allocation fails,
|
||
they will fallback to the global default memory area.
|
||
|
||
numa_cma=<node>:nn[MG][,<node>:nn[MG]]
|
||
[KNL,CMA,EARLY]
|
||
Sets the size of kernel numa memory area for
|
||
contiguous memory allocations. It will reserve CMA
|
||
area for the specified node.
|
||
|
||
With numa CMA enabled, DMA users on node nid will
|
||
first try to allocate buffer from the numa area
|
||
which is located in node nid, if the allocation fails,
|
||
they will fallback to the global default memory area.
|
||
|
||
cmo_free_hint= [PPC] Format: { yes | no }
|
||
Specify whether pages are marked as being inactive
|
||
when they are freed. This is used in CMO environments
|
||
to determine OS memory pressure for page stealing by
|
||
a hypervisor.
|
||
Default: yes
|
||
|
||
coherent_pool=nn[KMG] [ARM,KNL,EARLY]
|
||
Sets the size of memory pool for coherent, atomic dma
|
||
allocations, by default set to 256K.
|
||
|
||
com20020= [HW,NET] ARCnet - COM20020 chipset
|
||
Format:
|
||
<io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
|
||
|
||
com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
|
||
Format: <io>[,<irq>]
|
||
|
||
com90xx= [HW,NET]
|
||
ARCnet - COM90xx chipset (memory-mapped buffers)
|
||
Format: <io>[,<irq>[,<memstart>]]
|
||
|
||
condev= [HW,S390] console device
|
||
conmode=
|
||
|
||
con3215_drop= [S390,EARLY] 3215 console drop mode.
|
||
Format: y|n|Y|N|1|0
|
||
When set to true, drop data on the 3215 console when
|
||
the console buffer is full. In this case the
|
||
operator using a 3270 terminal emulator (for example
|
||
x3270) does not have to enter the clear key for the
|
||
console output to advance and the kernel to continue.
|
||
This leads to a much faster boot time when a 3270
|
||
terminal emulator is active. If no 3270 terminal
|
||
emulator is used, this parameter has no effect.
|
||
|
||
console= [KNL] Output console device and options.
|
||
|
||
tty<n> Use the virtual console device <n>.
|
||
|
||
ttyS<n>[,options]
|
||
ttyUSB0[,options]
|
||
Use the specified serial port. The options are of
|
||
the form "bbbbpnf", where "bbbb" is the baud rate,
|
||
"p" is parity ("n", "o", or "e"), "n" is number of
|
||
bits, and "f" is flow control ("r" for RTS or
|
||
omit it). Default is "9600n8".
|
||
|
||
See Documentation/admin-guide/serial-console.rst for more
|
||
information. See
|
||
Documentation/networking/netconsole.rst for an
|
||
alternative.
|
||
|
||
<DEVNAME>:<n>.<n>[,options]
|
||
Use the specified serial port on the serial core bus.
|
||
The addressing uses DEVNAME of the physical serial port
|
||
device, followed by the serial core controller instance,
|
||
and the serial port instance. The options are the same
|
||
as documented for the ttyS addressing above.
|
||
|
||
The mapping of the serial ports to the tty instances
|
||
can be viewed with:
|
||
|
||
$ ls -d /sys/bus/serial-base/devices/*:*.*/tty/*
|
||
/sys/bus/serial-base/devices/00:04:0.0/tty/ttyS0
|
||
|
||
In the above example, the console can be addressed with
|
||
console=00:04:0.0. Note that a console addressed this
|
||
way will only get added when the related device driver
|
||
is ready. The use of an earlycon parameter in addition to
|
||
the console may be desired for console output early on.
|
||
|
||
uart[8250],io,<addr>[,options]
|
||
uart[8250],mmio,<addr>[,options]
|
||
uart[8250],mmio16,<addr>[,options]
|
||
uart[8250],mmio32,<addr>[,options]
|
||
uart[8250],0x<addr>[,options]
|
||
Start an early, polled-mode console on the 8250/16550
|
||
UART at the specified I/O port or MMIO address,
|
||
switching to the matching ttyS device later.
|
||
MMIO inter-register address stride is either 8-bit
|
||
(mmio), 16-bit (mmio16), or 32-bit (mmio32).
|
||
If none of [io|mmio|mmio16|mmio32], <addr> is assumed
|
||
to be equivalent to 'mmio'. 'options' are specified in
|
||
the same format described for ttyS above; if unspecified,
|
||
the h/w is not re-initialized.
|
||
|
||
hvc<n> Use the hypervisor console device <n>. This is for
|
||
both Xen and PowerPC hypervisors.
|
||
|
||
{ null | "" }
|
||
Use to disable console output, i.e., to have kernel
|
||
console messages discarded.
|
||
This must be the only console= parameter used on the
|
||
kernel command line.
|
||
|
||
If the device connected to the port is not a TTY but a braille
|
||
device, prepend "brl," before the device type, for instance
|
||
console=brl,ttyS0
|
||
For now, only VisioBraille is supported.
|
||
|
||
console_msg_format=
|
||
[KNL] Change console messages format
|
||
default
|
||
By default we print messages on consoles in
|
||
"[time stamp] text\n" format (time stamp may not be
|
||
printed, depending on CONFIG_PRINTK_TIME or
|
||
`printk_time' param).
|
||
syslog
|
||
Switch to syslog format: "<%u>[time stamp] text\n"
|
||
IOW, each message will have a facility and loglevel
|
||
prefix. The format is similar to one used by syslog()
|
||
syscall, or to executing "dmesg -S --raw" or to reading
|
||
from /proc/kmsg.
|
||
|
||
consoleblank= [KNL] The console blank (screen saver) timeout in
|
||
seconds. A value of 0 disables the blank timer.
|
||
Defaults to 0.
|
||
|
||
coredump_filter=
|
||
[KNL] Change the default value for
|
||
/proc/<pid>/coredump_filter.
|
||
See also Documentation/filesystems/proc.rst.
|
||
|
||
coresight_cpu_debug.enable
|
||
[ARM,ARM64]
|
||
Format: <bool>
|
||
Enable/disable the CPU sampling based debugging.
|
||
0: default value, disable debugging
|
||
1: enable debugging at boot time
|
||
|
||
cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
|
||
Format:
|
||
<first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
|
||
|
||
cpuidle.off=1 [CPU_IDLE]
|
||
disable the cpuidle sub-system
|
||
|
||
cpuidle.governor=
|
||
[CPU_IDLE] Name of the cpuidle governor to use.
|
||
|
||
cpufreq.off=1 [CPU_FREQ]
|
||
disable the cpufreq sub-system
|
||
|
||
cpufreq.default_governor=
|
||
[CPU_FREQ] Name of the default cpufreq governor or
|
||
policy to use. This governor must be registered in the
|
||
kernel before the cpufreq driver probes.
|
||
|
||
cpu_init_udelay=N
|
||
[X86,EARLY] Delay for N microsec between assert and de-assert
|
||
of APIC INIT to start processors. This delay occurs
|
||
on every CPU online, such as boot, and resume from suspend.
|
||
Default: 10000
|
||
|
||
cpuhp.parallel=
|
||
[SMP] Enable/disable parallel bringup of secondary CPUs
|
||
Format: <bool>
|
||
Default is enabled if CONFIG_HOTPLUG_PARALLEL=y. Otherwise
|
||
the parameter has no effect.
|
||
|
||
crash_kexec_post_notifiers
|
||
Run kdump after running panic-notifiers and dumping
|
||
kmsg. This only for the users who doubt kdump always
|
||
succeeds in any situation.
|
||
Note that this also increases risks of kdump failure,
|
||
because some panic notifiers can make the crashed
|
||
kernel more unstable.
|
||
|
||
crashkernel=size[KMG][@offset[KMG]]
|
||
[KNL,EARLY] Using kexec, Linux can switch to a 'crash kernel'
|
||
upon panic. This parameter reserves the physical
|
||
memory region [offset, offset + size] for that kernel
|
||
image. If '@offset' is omitted, then a suitable offset
|
||
is selected automatically.
|
||
[KNL, X86-64, ARM64, RISCV, LoongArch] Select a region
|
||
under 4G first, and fall back to reserve region above
|
||
4G when '@offset' hasn't been specified.
|
||
See Documentation/admin-guide/kdump/kdump.rst for further details.
|
||
|
||
crashkernel=range1:size1[,range2:size2,...][@offset]
|
||
[KNL] Same as above, but depends on the memory
|
||
in the running system. The syntax of range is
|
||
start-[end] where start and end are both
|
||
a memory unit (amount[KMG]). See also
|
||
Documentation/admin-guide/kdump/kdump.rst for an example.
|
||
|
||
crashkernel=size[KMG],high
|
||
[KNL, X86-64, ARM64, RISCV, LoongArch] range could be
|
||
above 4G.
|
||
Allow kernel to allocate physical memory region from top,
|
||
so could be above 4G if system have more than 4G ram
|
||
installed. Otherwise memory region will be allocated
|
||
below 4G, if available.
|
||
It will be ignored if crashkernel=X is specified.
|
||
crashkernel=size[KMG],low
|
||
[KNL, X86-64, ARM64, RISCV, LoongArch] range under 4G.
|
||
When crashkernel=X,high is passed, kernel could allocate
|
||
physical memory region above 4G, that cause second kernel
|
||
crash on system that require some amount of low memory,
|
||
e.g. swiotlb requires at least 64M+32K low memory, also
|
||
enough extra low memory is needed to make sure DMA buffers
|
||
for 32-bit devices won't run out. Kernel would try to allocate
|
||
default size of memory below 4G automatically. The default
|
||
size is platform dependent.
|
||
--> x86: max(swiotlb_size_or_default() + 8MiB, 256MiB)
|
||
--> arm64: 128MiB
|
||
--> riscv: 128MiB
|
||
--> loongarch: 128MiB
|
||
This one lets the user specify own low range under 4G
|
||
for second kernel instead.
|
||
0: to disable low allocation.
|
||
It will be ignored when crashkernel=X,high is not used
|
||
or memory reserved is below 4G.
|
||
|
||
cryptomgr.notests
|
||
[KNL] Disable crypto self-tests
|
||
|
||
cs89x0_dma= [HW,NET]
|
||
Format: <dma>
|
||
|
||
cs89x0_media= [HW,NET]
|
||
Format: { rj45 | aui | bnc }
|
||
|
||
csdlock_debug= [KNL] Enable or disable debug add-ons of cross-CPU
|
||
function call handling. When switched on,
|
||
additional debug data is printed to the console
|
||
in case a hanging CPU is detected, and that
|
||
CPU is pinged again in order to try to resolve
|
||
the hang situation. The default value of this
|
||
option depends on the CSD_LOCK_WAIT_DEBUG_DEFAULT
|
||
Kconfig option.
|
||
|
||
dasd= [HW,NET]
|
||
See header of drivers/s390/block/dasd_devmap.c.
|
||
|
||
db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
|
||
(one device per port)
|
||
Format: <port#>,<type>
|
||
See also Documentation/input/devices/joystick-parport.rst
|
||
|
||
debug [KNL,EARLY] Enable kernel debugging (events log level).
|
||
|
||
debug_boot_weak_hash
|
||
[KNL,EARLY] Enable printing [hashed] pointers early in the
|
||
boot sequence. If enabled, we use a weak hash instead
|
||
of siphash to hash pointers. Use this option if you are
|
||
seeing instances of '(___ptrval___)') and need to see a
|
||
value (hashed pointer) instead. Cryptographically
|
||
insecure, please do not use on production kernels.
|
||
|
||
debug_locks_verbose=
|
||
[KNL] verbose locking self-tests
|
||
Format: <int>
|
||
Print debugging info while doing the locking API
|
||
self-tests.
|
||
Bitmask for the various LOCKTYPE_ tests. Defaults to 0
|
||
(no extra messages), setting it to -1 (all bits set)
|
||
will print _a_lot_ more information - normally only
|
||
useful to lockdep developers.
|
||
|
||
debug_objects [KNL,EARLY] Enable object debugging
|
||
|
||
debug_guardpage_minorder=
|
||
[KNL,EARLY] When CONFIG_DEBUG_PAGEALLOC is set, this
|
||
parameter allows control of the order of pages that will
|
||
be intentionally kept free (and hence protected) by the
|
||
buddy allocator. Bigger value increase the probability
|
||
of catching random memory corruption, but reduce the
|
||
amount of memory for normal system use. The maximum
|
||
possible value is MAX_PAGE_ORDER/2. Setting this
|
||
parameter to 1 or 2 should be enough to identify most
|
||
random memory corruption problems caused by bugs in
|
||
kernel or driver code when a CPU writes to (or reads
|
||
from) a random memory location. Note that there exists
|
||
a class of memory corruptions problems caused by buggy
|
||
H/W or F/W or by drivers badly programming DMA
|
||
(basically when memory is written at bus level and the
|
||
CPU MMU is bypassed) which are not detectable by
|
||
CONFIG_DEBUG_PAGEALLOC, hence this option will not
|
||
help tracking down these problems.
|
||
|
||
debug_pagealloc=
|
||
[KNL,EARLY] When CONFIG_DEBUG_PAGEALLOC is set, this parameter
|
||
enables the feature at boot time. By default, it is
|
||
disabled and the system will work mostly the same as a
|
||
kernel built without CONFIG_DEBUG_PAGEALLOC.
|
||
Note: to get most of debug_pagealloc error reports, it's
|
||
useful to also enable the page_owner functionality.
|
||
on: enable the feature
|
||
|
||
debugfs= [KNL,EARLY] This parameter enables what is exposed to
|
||
userspace and debugfs internal clients.
|
||
Format: { on, no-mount, off }
|
||
on: All functions are enabled.
|
||
no-mount:
|
||
Filesystem is not registered but kernel clients can
|
||
access APIs and a crashkernel can be used to read
|
||
its content. There is nothing to mount.
|
||
off: Filesystem is not registered and clients
|
||
get a -EPERM as result when trying to register files
|
||
or directories within debugfs.
|
||
This is equivalent of the runtime functionality if
|
||
debugfs was not enabled in the kernel at all.
|
||
Default value is set in build-time with a kernel configuration.
|
||
|
||
debugpat [X86] Enable PAT debugging
|
||
|
||
default_hugepagesz=
|
||
[HW] The size of the default HugeTLB page. This is
|
||
the size represented by the legacy /proc/ hugepages
|
||
APIs. In addition, this is the default hugetlb size
|
||
used for shmget(), mmap() and mounting hugetlbfs
|
||
filesystems. If not specified, defaults to the
|
||
architecture's default huge page size. Huge page
|
||
sizes are architecture dependent. See also
|
||
Documentation/admin-guide/mm/hugetlbpage.rst.
|
||
Format: size[KMG]
|
||
|
||
deferred_probe_timeout=
|
||
[KNL] Debugging option to set a timeout in seconds for
|
||
deferred probe to give up waiting on dependencies to
|
||
probe. Only specific dependencies (subsystems or
|
||
drivers) that have opted in will be ignored. A timeout
|
||
of 0 will timeout at the end of initcalls. If the time
|
||
out hasn't expired, it'll be restarted by each
|
||
successful driver registration. This option will also
|
||
dump out devices still on the deferred probe list after
|
||
retrying.
|
||
|
||
delayacct [KNL] Enable per-task delay accounting
|
||
|
||
dell_smm_hwmon.ignore_dmi=
|
||
[HW] Continue probing hardware even if DMI data
|
||
indicates that the driver is running on unsupported
|
||
hardware.
|
||
|
||
dell_smm_hwmon.force=
|
||
[HW] Activate driver even if SMM BIOS signature does
|
||
not match list of supported models and enable otherwise
|
||
blacklisted features.
|
||
|
||
dell_smm_hwmon.power_status=
|
||
[HW] Report power status in /proc/i8k
|
||
(disabled by default).
|
||
|
||
dell_smm_hwmon.restricted=
|
||
[HW] Allow controlling fans only if SYS_ADMIN
|
||
capability is set.
|
||
|
||
dell_smm_hwmon.fan_mult=
|
||
[HW] Factor to multiply fan speed with.
|
||
|
||
dell_smm_hwmon.fan_max=
|
||
[HW] Maximum configurable fan speed.
|
||
|
||
dfltcc= [HW,S390]
|
||
Format: { on | off | def_only | inf_only | always }
|
||
on: s390 zlib hardware support for compression on
|
||
level 1 and decompression (default)
|
||
off: No s390 zlib hardware support
|
||
def_only: s390 zlib hardware support for deflate
|
||
only (compression on level 1)
|
||
inf_only: s390 zlib hardware support for inflate
|
||
only (decompression)
|
||
always: Same as 'on' but ignores the selected compression
|
||
level always using hardware support (used for debugging)
|
||
|
||
dhash_entries= [KNL]
|
||
Set number of hash buckets for dentry cache.
|
||
|
||
disable_1tb_segments [PPC,EARLY]
|
||
Disables the use of 1TB hash page table segments. This
|
||
causes the kernel to fall back to 256MB segments which
|
||
can be useful when debugging issues that require an SLB
|
||
miss to occur.
|
||
|
||
disable= [IPV6]
|
||
See Documentation/networking/ipv6.rst.
|
||
|
||
disable_radix [PPC,EARLY]
|
||
Disable RADIX MMU mode on POWER9
|
||
|
||
disable_tlbie [PPC]
|
||
Disable TLBIE instruction. Currently does not work
|
||
with KVM, with HASH MMU, or with coherent accelerators.
|
||
|
||
disable_ddw [PPC/PSERIES,EARLY]
|
||
Disable Dynamic DMA Window support. Use this
|
||
to workaround buggy firmware.
|
||
|
||
disable_ipv6= [IPV6]
|
||
See Documentation/networking/ipv6.rst.
|
||
|
||
disable_mtrr_cleanup [X86,EARLY]
|
||
The kernel tries to adjust MTRR layout from continuous
|
||
to discrete, to make X server driver able to add WB
|
||
entry later. This parameter disables that.
|
||
|
||
disable_mtrr_trim [X86, Intel and AMD only,EARLY]
|
||
By default the kernel will trim any uncacheable
|
||
memory out of your available memory pool based on
|
||
MTRR settings. This parameter disables that behavior,
|
||
possibly causing your machine to run very slowly.
|
||
|
||
disable_timer_pin_1 [X86,EARLY]
|
||
Disable PIN 1 of APIC timer
|
||
Can be useful to work around chipset bugs.
|
||
|
||
dis_ucode_ldr [X86] Disable the microcode loader.
|
||
|
||
dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
|
||
this option disables the debugging code at boot.
|
||
|
||
dma_debug_entries=<number>
|
||
This option allows to tune the number of preallocated
|
||
entries for DMA-API debugging code. One entry is
|
||
required per DMA-API allocation. Use this if the
|
||
DMA-API debugging code disables itself because the
|
||
architectural default is too low.
|
||
|
||
dma_debug_driver=<driver_name>
|
||
With this option the DMA-API debugging driver
|
||
filter feature can be enabled at boot time. Just
|
||
pass the driver to filter for as the parameter.
|
||
The filter can be disabled or changed to another
|
||
driver later using sysfs.
|
||
|
||
reg_file_data_sampling=
|
||
[X86] Controls mitigation for Register File Data
|
||
Sampling (RFDS) vulnerability. RFDS is a CPU
|
||
vulnerability which may allow userspace to infer
|
||
kernel data values previously stored in floating point
|
||
registers, vector registers, or integer registers.
|
||
RFDS only affects Intel Atom processors.
|
||
|
||
on: Turns ON the mitigation.
|
||
off: Turns OFF the mitigation.
|
||
|
||
This parameter overrides the compile time default set
|
||
by CONFIG_MITIGATION_RFDS. Mitigation cannot be
|
||
disabled when other VERW based mitigations (like MDS)
|
||
are enabled. In order to disable RFDS mitigation all
|
||
VERW based mitigations need to be disabled.
|
||
|
||
For details see:
|
||
Documentation/admin-guide/hw-vuln/reg-file-data-sampling.rst
|
||
|
||
driver_async_probe= [KNL]
|
||
List of driver names to be probed asynchronously. *
|
||
matches with all driver names. If * is specified, the
|
||
rest of the listed driver names are those that will NOT
|
||
match the *.
|
||
Format: <driver_name1>,<driver_name2>...
|
||
|
||
drm.edid_firmware=[<connector>:]<file>[,[<connector>:]<file>]
|
||
Broken monitors, graphic adapters, KVMs and EDIDless
|
||
panels may send no or incorrect EDID data sets.
|
||
This parameter allows to specify an EDID data sets
|
||
in the /lib/firmware directory that are used instead.
|
||
An EDID data set will only be used for a particular
|
||
connector, if its name and a colon are prepended to
|
||
the EDID name. Each connector may use a unique EDID
|
||
data set by separating the files with a comma. An EDID
|
||
data set with no connector name will be used for
|
||
any connectors not explicitly specified.
|
||
|
||
dscc4.setup= [NET]
|
||
|
||
dt_cpu_ftrs= [PPC,EARLY]
|
||
Format: {"off" | "known"}
|
||
Control how the dt_cpu_ftrs device-tree binding is
|
||
used for CPU feature discovery and setup (if it
|
||
exists).
|
||
off: Do not use it, fall back to legacy cpu table.
|
||
known: Do not pass through unknown features to guests
|
||
or userspace, only those that the kernel is aware of.
|
||
|
||
dump_apple_properties [X86]
|
||
Dump name and content of EFI device properties on
|
||
x86 Macs. Useful for driver authors to determine
|
||
what data is available or for reverse-engineering.
|
||
|
||
dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
|
||
<module>.dyndbg[="val"]
|
||
Enable debug messages at boot time. See
|
||
Documentation/admin-guide/dynamic-debug-howto.rst
|
||
for details.
|
||
|
||
early_ioremap_debug [KNL,EARLY]
|
||
Enable debug messages in early_ioremap support. This
|
||
is useful for tracking down temporary early mappings
|
||
which are not unmapped.
|
||
|
||
earlycon= [KNL,EARLY] Output early console device and options.
|
||
|
||
When used with no options, the early console is
|
||
determined by stdout-path property in device tree's
|
||
chosen node or the ACPI SPCR table if supported by
|
||
the platform.
|
||
|
||
cdns,<addr>[,options]
|
||
Start an early, polled-mode console on a Cadence
|
||
(xuartps) serial port at the specified address. Only
|
||
supported option is baud rate. If baud rate is not
|
||
specified, the serial port must already be setup and
|
||
configured.
|
||
|
||
uart[8250],io,<addr>[,options[,uartclk]]
|
||
uart[8250],mmio,<addr>[,options[,uartclk]]
|
||
uart[8250],mmio32,<addr>[,options[,uartclk]]
|
||
uart[8250],mmio32be,<addr>[,options[,uartclk]]
|
||
uart[8250],0x<addr>[,options]
|
||
Start an early, polled-mode console on the 8250/16550
|
||
UART at the specified I/O port or MMIO address.
|
||
MMIO inter-register address stride is either 8-bit
|
||
(mmio) or 32-bit (mmio32 or mmio32be).
|
||
If none of [io|mmio|mmio32|mmio32be], <addr> is assumed
|
||
to be equivalent to 'mmio'. 'options' are specified
|
||
in the same format described for "console=ttyS<n>"; if
|
||
unspecified, the h/w is not initialized. 'uartclk' is
|
||
the uart clock frequency; if unspecified, it is set
|
||
to 'BASE_BAUD' * 16.
|
||
|
||
pl011,<addr>
|
||
pl011,mmio32,<addr>
|
||
Start an early, polled-mode console on a pl011 serial
|
||
port at the specified address. The pl011 serial port
|
||
must already be setup and configured. Options are not
|
||
yet supported. If 'mmio32' is specified, then only
|
||
the driver will use only 32-bit accessors to read/write
|
||
the device registers.
|
||
|
||
liteuart,<addr>
|
||
Start an early console on a litex serial port at the
|
||
specified address. The serial port must already be
|
||
setup and configured. Options are not yet supported.
|
||
|
||
meson,<addr>
|
||
Start an early, polled-mode console on a meson serial
|
||
port at the specified address. The serial port must
|
||
already be setup and configured. Options are not yet
|
||
supported.
|
||
|
||
msm_serial,<addr>
|
||
Start an early, polled-mode console on an msm serial
|
||
port at the specified address. The serial port
|
||
must already be setup and configured. Options are not
|
||
yet supported.
|
||
|
||
msm_serial_dm,<addr>
|
||
Start an early, polled-mode console on an msm serial
|
||
dm port at the specified address. The serial port
|
||
must already be setup and configured. Options are not
|
||
yet supported.
|
||
|
||
owl,<addr>
|
||
Start an early, polled-mode console on a serial port
|
||
of an Actions Semi SoC, such as S500 or S900, at the
|
||
specified address. The serial port must already be
|
||
setup and configured. Options are not yet supported.
|
||
|
||
rda,<addr>
|
||
Start an early, polled-mode console on a serial port
|
||
of an RDA Micro SoC, such as RDA8810PL, at the
|
||
specified address. The serial port must already be
|
||
setup and configured. Options are not yet supported.
|
||
|
||
sbi
|
||
Use RISC-V SBI (Supervisor Binary Interface) for early
|
||
console.
|
||
|
||
smh Use ARM semihosting calls for early console.
|
||
|
||
s3c2410,<addr>
|
||
s3c2412,<addr>
|
||
s3c2440,<addr>
|
||
s3c6400,<addr>
|
||
s5pv210,<addr>
|
||
exynos4210,<addr>
|
||
Use early console provided by serial driver available
|
||
on Samsung SoCs, requires selecting proper type and
|
||
a correct base address of the selected UART port. The
|
||
serial port must already be setup and configured.
|
||
Options are not yet supported.
|
||
|
||
lantiq,<addr>
|
||
Start an early, polled-mode console on a lantiq serial
|
||
(lqasc) port at the specified address. The serial port
|
||
must already be setup and configured. Options are not
|
||
yet supported.
|
||
|
||
lpuart,<addr>
|
||
lpuart32,<addr>
|
||
Use early console provided by Freescale LP UART driver
|
||
found on Freescale Vybrid and QorIQ LS1021A processors.
|
||
A valid base address must be provided, and the serial
|
||
port must already be setup and configured.
|
||
|
||
ec_imx21,<addr>
|
||
ec_imx6q,<addr>
|
||
Start an early, polled-mode, output-only console on the
|
||
Freescale i.MX UART at the specified address. The UART
|
||
must already be setup and configured.
|
||
|
||
ar3700_uart,<addr>
|
||
Start an early, polled-mode console on the
|
||
Armada 3700 serial port at the specified
|
||
address. The serial port must already be setup
|
||
and configured. Options are not yet supported.
|
||
|
||
qcom_geni,<addr>
|
||
Start an early, polled-mode console on a Qualcomm
|
||
Generic Interface (GENI) based serial port at the
|
||
specified address. The serial port must already be
|
||
setup and configured. Options are not yet supported.
|
||
|
||
efifb,[options]
|
||
Start an early, unaccelerated console on the EFI
|
||
memory mapped framebuffer (if available). On cache
|
||
coherent non-x86 systems that use system memory for
|
||
the framebuffer, pass the 'ram' option so that it is
|
||
mapped with the correct attributes.
|
||
|
||
linflex,<addr>
|
||
Use early console provided by Freescale LINFlexD UART
|
||
serial driver for NXP S32V234 SoCs. A valid base
|
||
address must be provided, and the serial port must
|
||
already be setup and configured.
|
||
|
||
earlyprintk= [X86,SH,ARM,M68k,S390,UM,EARLY]
|
||
earlyprintk=vga
|
||
earlyprintk=sclp
|
||
earlyprintk=xen
|
||
earlyprintk=serial[,ttySn[,baudrate]]
|
||
earlyprintk=serial[,0x...[,baudrate]]
|
||
earlyprintk=ttySn[,baudrate]
|
||
earlyprintk=dbgp[debugController#]
|
||
earlyprintk=pciserial[,force],bus:device.function[,baudrate]
|
||
earlyprintk=xdbc[xhciController#]
|
||
earlyprintk=bios
|
||
|
||
earlyprintk is useful when the kernel crashes before
|
||
the normal console is initialized. It is not enabled by
|
||
default because it has some cosmetic problems.
|
||
|
||
Append ",keep" to not disable it when the real console
|
||
takes over.
|
||
|
||
Only one of vga, serial, or usb debug port can
|
||
be used at a time.
|
||
|
||
Currently only ttyS0 and ttyS1 may be specified by
|
||
name. Other I/O ports may be explicitly specified
|
||
on some architectures (x86 and arm at least) by
|
||
replacing ttySn with an I/O port address, like this:
|
||
earlyprintk=serial,0x1008,115200
|
||
You can find the port for a given device in
|
||
/proc/tty/driver/serial:
|
||
2: uart:ST16650V2 port:00001008 irq:18 ...
|
||
|
||
Interaction with the standard serial driver is not
|
||
very good.
|
||
|
||
The VGA output is eventually overwritten by
|
||
the real console.
|
||
|
||
The xen option can only be used in Xen domains.
|
||
|
||
The sclp output can only be used on s390.
|
||
|
||
The bios output can only be used on SuperH.
|
||
|
||
The optional "force" to "pciserial" enables use of a
|
||
PCI device even when its classcode is not of the
|
||
UART class.
|
||
|
||
edac_report= [HW,EDAC] Control how to report EDAC event
|
||
Format: {"on" | "off" | "force"}
|
||
on: enable EDAC to report H/W event. May be overridden
|
||
by other higher priority error reporting module.
|
||
off: disable H/W event reporting through EDAC.
|
||
force: enforce the use of EDAC to report H/W event.
|
||
default: on.
|
||
|
||
edd= [EDD]
|
||
Format: {"off" | "on" | "skip[mbr]"}
|
||
|
||
efi= [EFI,EARLY]
|
||
Format: { "debug", "disable_early_pci_dma",
|
||
"nochunk", "noruntime", "nosoftreserve",
|
||
"novamap", "no_disable_early_pci_dma" }
|
||
debug: enable misc debug output.
|
||
disable_early_pci_dma: disable the busmaster bit on all
|
||
PCI bridges while in the EFI boot stub.
|
||
nochunk: disable reading files in "chunks" in the EFI
|
||
boot stub, as chunking can cause problems with some
|
||
firmware implementations.
|
||
noruntime : disable EFI runtime services support
|
||
nosoftreserve: The EFI_MEMORY_SP (Specific Purpose)
|
||
attribute may cause the kernel to reserve the
|
||
memory range for a memory mapping driver to
|
||
claim. Specify efi=nosoftreserve to disable this
|
||
reservation and treat the memory by its base type
|
||
(i.e. EFI_CONVENTIONAL_MEMORY / "System RAM").
|
||
novamap: do not call SetVirtualAddressMap().
|
||
no_disable_early_pci_dma: Leave the busmaster bit set
|
||
on all PCI bridges while in the EFI boot stub
|
||
|
||
efi_no_storage_paranoia [EFI,X86,EARLY]
|
||
Using this parameter you can use more than 50% of
|
||
your efi variable storage. Use this parameter only if
|
||
you are really sure that your UEFI does sane gc and
|
||
fulfills the spec otherwise your board may brick.
|
||
|
||
efivar_ssdt= [EFI; X86] Name of an EFI variable that contains an SSDT
|
||
that is to be dynamically loaded by Linux. If there are
|
||
multiple variables with the same name but with different
|
||
vendor GUIDs, all of them will be loaded. See
|
||
Documentation/admin-guide/acpi/ssdt-overlays.rst for details.
|
||
|
||
|
||
eisa_irq_edge= [PARISC,HW]
|
||
See header of drivers/parisc/eisa.c.
|
||
|
||
ekgdboc= [X86,KGDB,EARLY] Allow early kernel console debugging
|
||
Format: ekgdboc=kbd
|
||
|
||
This is designed to be used in conjunction with
|
||
the boot argument: earlyprintk=vga
|
||
|
||
This parameter works in place of the kgdboc parameter
|
||
but can only be used if the backing tty is available
|
||
very early in the boot process. For early debugging
|
||
via a serial port see kgdboc_earlycon instead.
|
||
|
||
elanfreq= [X86-32]
|
||
See comment before function elanfreq_setup() in
|
||
arch/x86/kernel/cpu/cpufreq/elanfreq.c.
|
||
|
||
elfcorehdr=[size[KMG]@]offset[KMG] [PPC,SH,X86,S390,EARLY]
|
||
Specifies physical address of start of kernel core
|
||
image elf header and optionally the size. Generally
|
||
kexec loader will pass this option to capture kernel.
|
||
See Documentation/admin-guide/kdump/kdump.rst for details.
|
||
|
||
enable_mtrr_cleanup [X86,EARLY]
|
||
The kernel tries to adjust MTRR layout from continuous
|
||
to discrete, to make X server driver able to add WB
|
||
entry later. This parameter enables that.
|
||
|
||
enable_timer_pin_1 [X86]
|
||
Enable PIN 1 of APIC timer
|
||
Can be useful to work around chipset bugs
|
||
(in particular on some ATI chipsets).
|
||
The kernel tries to set a reasonable default.
|
||
|
||
enforcing= [SELINUX] Set initial enforcing status.
|
||
Format: {"0" | "1"}
|
||
See security/selinux/Kconfig help text.
|
||
0 -- permissive (log only, no denials).
|
||
1 -- enforcing (deny and log).
|
||
Default value is 0.
|
||
Value can be changed at runtime via
|
||
/sys/fs/selinux/enforce.
|
||
|
||
erst_disable [ACPI]
|
||
Disable Error Record Serialization Table (ERST)
|
||
support.
|
||
|
||
ether= [HW,NET] Ethernet cards parameters
|
||
This option is obsoleted by the "netdev=" option, which
|
||
has equivalent usage. See its documentation for details.
|
||
|
||
evm= [EVM]
|
||
Format: { "fix" }
|
||
Permit 'security.evm' to be updated regardless of
|
||
current integrity status.
|
||
|
||
early_page_ext [KNL,EARLY] Enforces page_ext initialization to earlier
|
||
stages so cover more early boot allocations.
|
||
Please note that as side effect some optimizations
|
||
might be disabled to achieve that (e.g. parallelized
|
||
memory initialization is disabled) so the boot process
|
||
might take longer, especially on systems with a lot of
|
||
memory. Available with CONFIG_PAGE_EXTENSION=y.
|
||
|
||
failslab=
|
||
fail_usercopy=
|
||
fail_page_alloc=
|
||
fail_make_request=[KNL]
|
||
General fault injection mechanism.
|
||
Format: <interval>,<probability>,<space>,<times>
|
||
See also Documentation/fault-injection/.
|
||
|
||
fb_tunnels= [NET]
|
||
Format: { initns | none }
|
||
See Documentation/admin-guide/sysctl/net.rst for
|
||
fb_tunnels_only_for_init_ns
|
||
|
||
floppy= [HW]
|
||
See Documentation/admin-guide/blockdev/floppy.rst.
|
||
|
||
forcepae [X86-32]
|
||
Forcefully enable Physical Address Extension (PAE).
|
||
Many Pentium M systems disable PAE but may have a
|
||
functionally usable PAE implementation.
|
||
Warning: use of this parameter will taint the kernel
|
||
and may cause unknown problems.
|
||
|
||
fred= [X86-64]
|
||
Enable/disable Flexible Return and Event Delivery.
|
||
Format: { on | off }
|
||
on: enable FRED when it's present.
|
||
off: disable FRED, the default setting.
|
||
|
||
ftrace=[tracer]
|
||
[FTRACE] will set and start the specified tracer
|
||
as early as possible in order to facilitate early
|
||
boot debugging.
|
||
|
||
ftrace_boot_snapshot
|
||
[FTRACE] On boot up, a snapshot will be taken of the
|
||
ftrace ring buffer that can be read at:
|
||
/sys/kernel/tracing/snapshot.
|
||
This is useful if you need tracing information from kernel
|
||
boot up that is likely to be overridden by user space
|
||
start up functionality.
|
||
|
||
Optionally, the snapshot can also be defined for a tracing
|
||
instance that was created by the trace_instance= command
|
||
line parameter.
|
||
|
||
trace_instance=foo,sched_switch ftrace_boot_snapshot=foo
|
||
|
||
The above will cause the "foo" tracing instance to trigger
|
||
a snapshot at the end of boot up.
|
||
|
||
ftrace_dump_on_oops[=2(orig_cpu) | =<instance>][,<instance> |
|
||
,<instance>=2(orig_cpu)]
|
||
[FTRACE] will dump the trace buffers on oops.
|
||
If no parameter is passed, ftrace will dump global
|
||
buffers of all CPUs, if you pass 2 or orig_cpu, it
|
||
will dump only the buffer of the CPU that triggered
|
||
the oops, or the specific instance will be dumped if
|
||
its name is passed. Multiple instance dump is also
|
||
supported, and instances are separated by commas. Each
|
||
instance supports only dump on CPU that triggered the
|
||
oops by passing 2 or orig_cpu to it.
|
||
|
||
ftrace_dump_on_oops=foo=orig_cpu
|
||
|
||
The above will dump only the buffer of "foo" instance
|
||
on CPU that triggered the oops.
|
||
|
||
ftrace_dump_on_oops,foo,bar=orig_cpu
|
||
|
||
The above will dump global buffer on all CPUs, the
|
||
buffer of "foo" instance on all CPUs and the buffer
|
||
of "bar" instance on CPU that triggered the oops.
|
||
|
||
ftrace_filter=[function-list]
|
||
[FTRACE] Limit the functions traced by the function
|
||
tracer at boot up. function-list is a comma-separated
|
||
list of functions. This list can be changed at run
|
||
time by the set_ftrace_filter file in the debugfs
|
||
tracing directory.
|
||
|
||
ftrace_notrace=[function-list]
|
||
[FTRACE] Do not trace the functions specified in
|
||
function-list. This list can be changed at run time
|
||
by the set_ftrace_notrace file in the debugfs
|
||
tracing directory.
|
||
|
||
ftrace_graph_filter=[function-list]
|
||
[FTRACE] Limit the top level callers functions traced
|
||
by the function graph tracer at boot up.
|
||
function-list is a comma-separated list of functions
|
||
that can be changed at run time by the
|
||
set_graph_function file in the debugfs tracing directory.
|
||
|
||
ftrace_graph_notrace=[function-list]
|
||
[FTRACE] Do not trace from the functions specified in
|
||
function-list. This list is a comma-separated list of
|
||
functions that can be changed at run time by the
|
||
set_graph_notrace file in the debugfs tracing directory.
|
||
|
||
ftrace_graph_max_depth=<uint>
|
||
[FTRACE] Used with the function graph tracer. This is
|
||
the max depth it will trace into a function. This value
|
||
can be changed at run time by the max_graph_depth file
|
||
in the tracefs tracing directory. default: 0 (no limit)
|
||
|
||
fw_devlink= [KNL,EARLY] Create device links between consumer and supplier
|
||
devices by scanning the firmware to infer the
|
||
consumer/supplier relationships. This feature is
|
||
especially useful when drivers are loaded as modules as
|
||
it ensures proper ordering of tasks like device probing
|
||
(suppliers first, then consumers), supplier boot state
|
||
clean up (only after all consumers have probed),
|
||
suspend/resume & runtime PM (consumers first, then
|
||
suppliers).
|
||
Format: { off | permissive | on | rpm }
|
||
off -- Don't create device links from firmware info.
|
||
permissive -- Create device links from firmware info
|
||
but use it only for ordering boot state clean
|
||
up (sync_state() calls).
|
||
on -- Create device links from firmware info and use it
|
||
to enforce probe and suspend/resume ordering.
|
||
rpm -- Like "on", but also use to order runtime PM.
|
||
|
||
fw_devlink.strict=<bool>
|
||
[KNL,EARLY] Treat all inferred dependencies as mandatory
|
||
dependencies. This only applies for fw_devlink=on|rpm.
|
||
Format: <bool>
|
||
|
||
fw_devlink.sync_state =
|
||
[KNL,EARLY] When all devices that could probe have finished
|
||
probing, this parameter controls what to do with
|
||
devices that haven't yet received their sync_state()
|
||
calls.
|
||
Format: { strict | timeout }
|
||
strict -- Default. Continue waiting on consumers to
|
||
probe successfully.
|
||
timeout -- Give up waiting on consumers and call
|
||
sync_state() on any devices that haven't yet
|
||
received their sync_state() calls after
|
||
deferred_probe_timeout has expired or by
|
||
late_initcall() if !CONFIG_MODULES.
|
||
|
||
gamecon.map[2|3]=
|
||
[HW,JOY] Multisystem joystick and NES/SNES/PSX pad
|
||
support via parallel port (up to 5 devices per port)
|
||
Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
|
||
See also Documentation/input/devices/joystick-parport.rst
|
||
|
||
gamma= [HW,DRM]
|
||
|
||
gart_fix_e820= [X86-64,EARLY] disable the fix e820 for K8 GART
|
||
Format: off | on
|
||
default: on
|
||
|
||
gather_data_sampling=
|
||
[X86,INTEL,EARLY] Control the Gather Data Sampling (GDS)
|
||
mitigation.
|
||
|
||
Gather Data Sampling is a hardware vulnerability which
|
||
allows unprivileged speculative access to data which was
|
||
previously stored in vector registers.
|
||
|
||
This issue is mitigated by default in updated microcode.
|
||
The mitigation may have a performance impact but can be
|
||
disabled. On systems without the microcode mitigation
|
||
disabling AVX serves as a mitigation.
|
||
|
||
force: Disable AVX to mitigate systems without
|
||
microcode mitigation. No effect if the microcode
|
||
mitigation is present. Known to cause crashes in
|
||
userspace with buggy AVX enumeration.
|
||
|
||
off: Disable GDS mitigation.
|
||
|
||
gcov_persist= [GCOV] When non-zero (default), profiling data for
|
||
kernel modules is saved and remains accessible via
|
||
debugfs, even when the module is unloaded/reloaded.
|
||
When zero, profiling data is discarded and associated
|
||
debugfs files are removed at module unload time.
|
||
|
||
goldfish [X86] Enable the goldfish android emulator platform.
|
||
Don't use this when you are not running on the
|
||
android emulator
|
||
|
||
gpio-mockup.gpio_mockup_ranges
|
||
[HW] Sets the ranges of gpiochip of for this device.
|
||
Format: <start1>,<end1>,<start2>,<end2>...
|
||
gpio-mockup.gpio_mockup_named_lines
|
||
[HW] Let the driver know GPIO lines should be named.
|
||
|
||
gpt [EFI] Forces disk with valid GPT signature but
|
||
invalid Protective MBR to be treated as GPT. If the
|
||
primary GPT is corrupted, it enables the backup/alternate
|
||
GPT to be used instead.
|
||
|
||
grcan.enable0= [HW] Configuration of physical interface 0. Determines
|
||
the "Enable 0" bit of the configuration register.
|
||
Format: 0 | 1
|
||
Default: 0
|
||
grcan.enable1= [HW] Configuration of physical interface 1. Determines
|
||
the "Enable 0" bit of the configuration register.
|
||
Format: 0 | 1
|
||
Default: 0
|
||
grcan.select= [HW] Select which physical interface to use.
|
||
Format: 0 | 1
|
||
Default: 0
|
||
grcan.txsize= [HW] Sets the size of the tx buffer.
|
||
Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
|
||
Default: 1024
|
||
grcan.rxsize= [HW] Sets the size of the rx buffer.
|
||
Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
|
||
Default: 1024
|
||
|
||
hardened_usercopy=
|
||
[KNL] Under CONFIG_HARDENED_USERCOPY, whether
|
||
hardening is enabled for this boot. Hardened
|
||
usercopy checking is used to protect the kernel
|
||
from reading or writing beyond known memory
|
||
allocation boundaries as a proactive defense
|
||
against bounds-checking flaws in the kernel's
|
||
copy_to_user()/copy_from_user() interface.
|
||
on Perform hardened usercopy checks (default).
|
||
off Disable hardened usercopy checks.
|
||
|
||
hardlockup_all_cpu_backtrace=
|
||
[KNL] Should the hard-lockup detector generate
|
||
backtraces on all cpus.
|
||
Format: 0 | 1
|
||
|
||
hashdist= [KNL,NUMA] Large hashes allocated during boot
|
||
are distributed across NUMA nodes. Defaults on
|
||
for 64-bit NUMA, off otherwise.
|
||
Format: 0 | 1 (for off | on)
|
||
|
||
hd= [EIDE] (E)IDE hard drive subsystem geometry
|
||
Format: <cyl>,<head>,<sect>
|
||
|
||
hest_disable [ACPI]
|
||
Disable Hardware Error Source Table (HEST) support;
|
||
corresponding firmware-first mode error processing
|
||
logic will be disabled.
|
||
|
||
hibernate= [HIBERNATION]
|
||
noresume Don't check if there's a hibernation image
|
||
present during boot.
|
||
nocompress Don't compress/decompress hibernation images.
|
||
no Disable hibernation and resume.
|
||
protect_image Turn on image protection during restoration
|
||
(that will set all pages holding image data
|
||
during restoration read-only).
|
||
|
||
hibernate.compressor= [HIBERNATION] Compression algorithm to be
|
||
used with hibernation.
|
||
Format: { lzo | lz4 }
|
||
Default: lzo
|
||
|
||
lzo: Select LZO compression algorithm to
|
||
compress/decompress hibernation image.
|
||
|
||
lz4: Select LZ4 compression algorithm to
|
||
compress/decompress hibernation image.
|
||
|
||
highmem=nn[KMG] [KNL,BOOT,EARLY] forces the highmem zone to have an exact
|
||
size of <nn>. This works even on boxes that have no
|
||
highmem otherwise. This also works to reduce highmem
|
||
size on bigger boxes.
|
||
|
||
highres= [KNL] Enable/disable high resolution timer mode.
|
||
Valid parameters: "on", "off"
|
||
Default: "on"
|
||
|
||
hlt [BUGS=ARM,SH]
|
||
|
||
hostname= [KNL,EARLY] Set the hostname (aka UTS nodename).
|
||
Format: <string>
|
||
This allows setting the system's hostname during early
|
||
startup. This sets the name returned by gethostname.
|
||
Using this parameter to set the hostname makes it
|
||
possible to ensure the hostname is correctly set before
|
||
any userspace processes run, avoiding the possibility
|
||
that a process may call gethostname before the hostname
|
||
has been explicitly set, resulting in the calling
|
||
process getting an incorrect result. The string must
|
||
not exceed the maximum allowed hostname length (usually
|
||
64 characters) and will be truncated otherwise.
|
||
|
||
hpet= [X86-32,HPET] option to control HPET usage
|
||
Format: { enable (default) | disable | force |
|
||
verbose }
|
||
disable: disable HPET and use PIT instead
|
||
force: allow force enabled of undocumented chips (ICH4,
|
||
VIA, nVidia)
|
||
verbose: show contents of HPET registers during setup
|
||
|
||
hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET
|
||
registers. Default set by CONFIG_HPET_MMAP_DEFAULT.
|
||
|
||
hugepages= [HW] Number of HugeTLB pages to allocate at boot.
|
||
If this follows hugepagesz (below), it specifies
|
||
the number of pages of hugepagesz to be allocated.
|
||
If this is the first HugeTLB parameter on the command
|
||
line, it specifies the number of pages to allocate for
|
||
the default huge page size. If using node format, the
|
||
number of pages to allocate per-node can be specified.
|
||
See also Documentation/admin-guide/mm/hugetlbpage.rst.
|
||
Format: <integer> or (node format)
|
||
<node>:<integer>[,<node>:<integer>]
|
||
|
||
hugepagesz=
|
||
[HW] The size of the HugeTLB pages. This is used in
|
||
conjunction with hugepages (above) to allocate huge
|
||
pages of a specific size at boot. The pair
|
||
hugepagesz=X hugepages=Y can be specified once for
|
||
each supported huge page size. Huge page sizes are
|
||
architecture dependent. See also
|
||
Documentation/admin-guide/mm/hugetlbpage.rst.
|
||
Format: size[KMG]
|
||
|
||
hugetlb_cma= [HW,CMA,EARLY] The size of a CMA area used for allocation
|
||
of gigantic hugepages. Or using node format, the size
|
||
of a CMA area per node can be specified.
|
||
Format: nn[KMGTPE] or (node format)
|
||
<node>:nn[KMGTPE][,<node>:nn[KMGTPE]]
|
||
|
||
Reserve a CMA area of given size and allocate gigantic
|
||
hugepages using the CMA allocator. If enabled, the
|
||
boot-time allocation of gigantic hugepages is skipped.
|
||
|
||
hugetlb_free_vmemmap=
|
||
[KNL] Requires CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP
|
||
enabled.
|
||
Control if HugeTLB Vmemmap Optimization (HVO) is enabled.
|
||
Allows heavy hugetlb users to free up some more
|
||
memory (7 * PAGE_SIZE for each 2MB hugetlb page).
|
||
Format: { on | off (default) }
|
||
|
||
on: enable HVO
|
||
off: disable HVO
|
||
|
||
Built with CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP_DEFAULT_ON=y,
|
||
the default is on.
|
||
|
||
Note that the vmemmap pages may be allocated from the added
|
||
memory block itself when memory_hotplug.memmap_on_memory is
|
||
enabled, those vmemmap pages cannot be optimized even if this
|
||
feature is enabled. Other vmemmap pages not allocated from
|
||
the added memory block itself do not be affected.
|
||
|
||
hung_task_panic=
|
||
[KNL] Should the hung task detector generate panics.
|
||
Format: 0 | 1
|
||
|
||
A value of 1 instructs the kernel to panic when a
|
||
hung task is detected. The default value is controlled
|
||
by the CONFIG_BOOTPARAM_HUNG_TASK_PANIC build-time
|
||
option. The value selected by this boot parameter can
|
||
be changed later by the kernel.hung_task_panic sysctl.
|
||
|
||
hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
|
||
terminal devices. Valid values: 0..8
|
||
hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
|
||
If specified, z/VM IUCV HVC accepts connections
|
||
from listed z/VM user IDs only.
|
||
|
||
hv_nopvspin [X86,HYPER_V,EARLY]
|
||
Disables the paravirt spinlock optimizations
|
||
which allow the hypervisor to 'idle' the guest
|
||
on lock contention.
|
||
|
||
i2c_bus= [HW] Override the default board specific I2C bus speed
|
||
or register an additional I2C bus that is not
|
||
registered from board initialization code.
|
||
Format:
|
||
<bus_id>,<clkrate>
|
||
|
||
i2c_touchscreen_props= [HW,ACPI,X86]
|
||
Set device-properties for ACPI-enumerated I2C-attached
|
||
touchscreen, to e.g. fix coordinates of upside-down
|
||
mounted touchscreens. If you need this option please
|
||
submit a drivers/platform/x86/touchscreen_dmi.c patch
|
||
adding a DMI quirk for this.
|
||
|
||
Format:
|
||
<ACPI_HW_ID>:<prop_name>=<val>[:prop_name=val][:...]
|
||
Where <val> is one of:
|
||
Omit "=<val>" entirely Set a boolean device-property
|
||
Unsigned number Set a u32 device-property
|
||
Anything else Set a string device-property
|
||
|
||
Examples (split over multiple lines):
|
||
i2c_touchscreen_props=GDIX1001:touchscreen-inverted-x:
|
||
touchscreen-inverted-y
|
||
|
||
i2c_touchscreen_props=MSSL1680:touchscreen-size-x=1920:
|
||
touchscreen-size-y=1080:touchscreen-inverted-y:
|
||
firmware-name=gsl1680-vendor-model.fw:silead,home-button
|
||
|
||
i8042.debug [HW] Toggle i8042 debug mode
|
||
i8042.unmask_kbd_data
|
||
[HW] Enable printing of interrupt data from the KBD port
|
||
(disabled by default, and as a pre-condition
|
||
requires that i8042.debug=1 be enabled)
|
||
i8042.direct [HW] Put keyboard port into non-translated mode
|
||
i8042.dumbkbd [HW] Pretend that controller can only read data from
|
||
keyboard and cannot control its state
|
||
(Don't attempt to blink the leds)
|
||
i8042.noaux [HW] Don't check for auxiliary (== mouse) port
|
||
i8042.nokbd [HW] Don't check/create keyboard port
|
||
i8042.noloop [HW] Disable the AUX Loopback command while probing
|
||
for the AUX port
|
||
i8042.nomux [HW] Don't check presence of an active multiplexing
|
||
controller
|
||
i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
|
||
controllers
|
||
i8042.notimeout [HW] Ignore timeout condition signalled by controller
|
||
i8042.reset [HW] Reset the controller during init, cleanup and
|
||
suspend-to-ram transitions, only during s2r
|
||
transitions, or never reset
|
||
Format: { 1 | Y | y | 0 | N | n }
|
||
1, Y, y: always reset controller
|
||
0, N, n: don't ever reset controller
|
||
Default: only on s2r transitions on x86; most other
|
||
architectures force reset to be always executed
|
||
i8042.unlock [HW] Unlock (ignore) the keylock
|
||
i8042.kbdreset [HW] Reset device connected to KBD port
|
||
i8042.probe_defer
|
||
[HW] Allow deferred probing upon i8042 probe errors
|
||
|
||
i810= [HW,DRM]
|
||
|
||
i915.invert_brightness=
|
||
[DRM] Invert the sense of the variable that is used to
|
||
set the brightness of the panel backlight. Normally a
|
||
brightness value of 0 indicates backlight switched off,
|
||
and the maximum of the brightness value sets the backlight
|
||
to maximum brightness. If this parameter is set to 0
|
||
(default) and the machine requires it, or this parameter
|
||
is set to 1, a brightness value of 0 sets the backlight
|
||
to maximum brightness, and the maximum of the brightness
|
||
value switches the backlight off.
|
||
-1 -- never invert brightness
|
||
0 -- machine default
|
||
1 -- force brightness inversion
|
||
|
||
ia32_emulation= [X86-64]
|
||
Format: <bool>
|
||
When true, allows loading 32-bit programs and executing 32-bit
|
||
syscalls, essentially overriding IA32_EMULATION_DEFAULT_DISABLED at
|
||
boot time. When false, unconditionally disables IA32 emulation.
|
||
|
||
icn= [HW,ISDN]
|
||
Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
|
||
|
||
|
||
idle= [X86,EARLY]
|
||
Format: idle=poll, idle=halt, idle=nomwait
|
||
Poll forces a polling idle loop that can slightly
|
||
improve the performance of waking up a idle CPU, but
|
||
will use a lot of power and make the system run hot.
|
||
Not recommended.
|
||
idle=halt: Halt is forced to be used for CPU idle.
|
||
In such case C2/C3 won't be used again.
|
||
idle=nomwait: Disable mwait for CPU C-states
|
||
|
||
idxd.sva= [HW]
|
||
Format: <bool>
|
||
Allow force disabling of Shared Virtual Memory (SVA)
|
||
support for the idxd driver. By default it is set to
|
||
true (1).
|
||
|
||
idxd.tc_override= [HW]
|
||
Format: <bool>
|
||
Allow override of default traffic class configuration
|
||
for the device. By default it is set to false (0).
|
||
|
||
ieee754= [MIPS] Select IEEE Std 754 conformance mode
|
||
Format: { strict | legacy | 2008 | relaxed | emulated }
|
||
Default: strict
|
||
|
||
Choose which programs will be accepted for execution
|
||
based on the IEEE 754 NaN encoding(s) supported by
|
||
the FPU and the NaN encoding requested with the value
|
||
of an ELF file header flag individually set by each
|
||
binary. Hardware implementations are permitted to
|
||
support either or both of the legacy and the 2008 NaN
|
||
encoding mode.
|
||
|
||
Available settings are as follows:
|
||
strict accept binaries that request a NaN encoding
|
||
supported by the FPU
|
||
legacy only accept legacy-NaN binaries, if supported
|
||
by the FPU
|
||
2008 only accept 2008-NaN binaries, if supported
|
||
by the FPU
|
||
relaxed accept any binaries regardless of whether
|
||
supported by the FPU
|
||
emulated accept any binaries but enable FPU emulator
|
||
if binary mode is unsupported by the FPU.
|
||
|
||
The FPU emulator is always able to support both NaN
|
||
encodings, so if no FPU hardware is present or it has
|
||
been disabled with 'nofpu', then the settings of
|
||
'legacy' and '2008' strap the emulator accordingly,
|
||
'relaxed' straps the emulator for both legacy-NaN and
|
||
2008-NaN, whereas 'strict' enables legacy-NaN only on
|
||
legacy processors and both NaN encodings on MIPS32 or
|
||
MIPS64 CPUs.
|
||
|
||
The setting for ABS.fmt/NEG.fmt instruction execution
|
||
mode generally follows that for the NaN encoding,
|
||
except where unsupported by hardware.
|
||
|
||
ignore_loglevel [KNL,EARLY]
|
||
Ignore loglevel setting - this will print /all/
|
||
kernel messages to the console. Useful for debugging.
|
||
We also add it as printk module parameter, so users
|
||
could change it dynamically, usually by
|
||
/sys/module/printk/parameters/ignore_loglevel.
|
||
|
||
ignore_rlimit_data
|
||
Ignore RLIMIT_DATA setting for data mappings,
|
||
print warning at first misuse. Can be changed via
|
||
/sys/module/kernel/parameters/ignore_rlimit_data.
|
||
|
||
ihash_entries= [KNL]
|
||
Set number of hash buckets for inode cache.
|
||
|
||
ima_appraise= [IMA] appraise integrity measurements
|
||
Format: { "off" | "enforce" | "fix" | "log" }
|
||
default: "enforce"
|
||
|
||
ima_appraise_tcb [IMA] Deprecated. Use ima_policy= instead.
|
||
The builtin appraise policy appraises all files
|
||
owned by uid=0.
|
||
|
||
ima_canonical_fmt [IMA]
|
||
Use the canonical format for the binary runtime
|
||
measurements, instead of host native format.
|
||
|
||
ima_hash= [IMA]
|
||
Format: { md5 | sha1 | rmd160 | sha256 | sha384
|
||
| sha512 | ... }
|
||
default: "sha1"
|
||
|
||
The list of supported hash algorithms is defined
|
||
in crypto/hash_info.h.
|
||
|
||
ima_policy= [IMA]
|
||
The builtin policies to load during IMA setup.
|
||
Format: "tcb | appraise_tcb | secure_boot |
|
||
fail_securely | critical_data"
|
||
|
||
The "tcb" policy measures all programs exec'd, files
|
||
mmap'd for exec, and all files opened with the read
|
||
mode bit set by either the effective uid (euid=0) or
|
||
uid=0.
|
||
|
||
The "appraise_tcb" policy appraises the integrity of
|
||
all files owned by root.
|
||
|
||
The "secure_boot" policy appraises the integrity
|
||
of files (eg. kexec kernel image, kernel modules,
|
||
firmware, policy, etc) based on file signatures.
|
||
|
||
The "fail_securely" policy forces file signature
|
||
verification failure also on privileged mounted
|
||
filesystems with the SB_I_UNVERIFIABLE_SIGNATURE
|
||
flag.
|
||
|
||
The "critical_data" policy measures kernel integrity
|
||
critical data.
|
||
|
||
ima_tcb [IMA] Deprecated. Use ima_policy= instead.
|
||
Load a policy which meets the needs of the Trusted
|
||
Computing Base. This means IMA will measure all
|
||
programs exec'd, files mmap'd for exec, and all files
|
||
opened for read by uid=0.
|
||
|
||
ima_template= [IMA]
|
||
Select one of defined IMA measurements template formats.
|
||
Formats: { "ima" | "ima-ng" | "ima-ngv2" | "ima-sig" |
|
||
"ima-sigv2" }
|
||
Default: "ima-ng"
|
||
|
||
ima_template_fmt=
|
||
[IMA] Define a custom template format.
|
||
Format: { "field1|...|fieldN" }
|
||
|
||
ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage
|
||
Format: <min_file_size>
|
||
Set the minimal file size for using asynchronous hash.
|
||
If left unspecified, ahash usage is disabled.
|
||
|
||
ahash performance varies for different data sizes on
|
||
different crypto accelerators. This option can be used
|
||
to achieve the best performance for a particular HW.
|
||
|
||
ima.ahash_bufsize= [IMA] Asynchronous hash buffer size
|
||
Format: <bufsize>
|
||
Set hashing buffer size. Default: 4k.
|
||
|
||
ahash performance varies for different chunk sizes on
|
||
different crypto accelerators. This option can be used
|
||
to achieve best performance for particular HW.
|
||
|
||
init= [KNL]
|
||
Format: <full_path>
|
||
Run specified binary instead of /sbin/init as init
|
||
process.
|
||
|
||
initcall_debug [KNL] Trace initcalls as they are executed. Useful
|
||
for working out where the kernel is dying during
|
||
startup.
|
||
|
||
initcall_blacklist= [KNL] Do not execute a comma-separated list of
|
||
initcall functions. Useful for debugging built-in
|
||
modules and initcalls.
|
||
|
||
initramfs_async= [KNL]
|
||
Format: <bool>
|
||
Default: 1
|
||
This parameter controls whether the initramfs
|
||
image is unpacked asynchronously, concurrently
|
||
with devices being probed and
|
||
initialized. This should normally just work,
|
||
but as a debugging aid, one can get the
|
||
historical behaviour of the initramfs
|
||
unpacking being completed before device_ and
|
||
late_ initcalls.
|
||
|
||
initrd= [BOOT,EARLY] Specify the location of the initial ramdisk
|
||
|
||
initrdmem= [KNL,EARLY] Specify a physical address and size from which to
|
||
load the initrd. If an initrd is compiled in or
|
||
specified in the bootparams, it takes priority over this
|
||
setting.
|
||
Format: ss[KMG],nn[KMG]
|
||
Default is 0, 0
|
||
|
||
init_on_alloc= [MM,EARLY] Fill newly allocated pages and heap objects with
|
||
zeroes.
|
||
Format: 0 | 1
|
||
Default set by CONFIG_INIT_ON_ALLOC_DEFAULT_ON.
|
||
|
||
init_on_free= [MM,EARLY] Fill freed pages and heap objects with zeroes.
|
||
Format: 0 | 1
|
||
Default set by CONFIG_INIT_ON_FREE_DEFAULT_ON.
|
||
|
||
init_pkru= [X86] Specify the default memory protection keys rights
|
||
register contents for all processes. 0x55555554 by
|
||
default (disallow access to all but pkey 0). Can
|
||
override in debugfs after boot.
|
||
|
||
inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
|
||
Format: <irq>
|
||
|
||
int_pln_enable [X86] Enable power limit notification interrupt
|
||
|
||
integrity_audit=[IMA]
|
||
Format: { "0" | "1" }
|
||
0 -- basic integrity auditing messages. (Default)
|
||
1 -- additional integrity auditing messages.
|
||
|
||
intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
|
||
on
|
||
Enable intel iommu driver.
|
||
off
|
||
Disable intel iommu driver.
|
||
igfx_off [Default Off]
|
||
By default, gfx is mapped as normal device. If a gfx
|
||
device has a dedicated DMAR unit, the DMAR unit is
|
||
bypassed by not enabling DMAR with this option. In
|
||
this case, gfx device will use physical address for
|
||
DMA.
|
||
strict [Default Off]
|
||
Deprecated, equivalent to iommu.strict=1.
|
||
sp_off [Default Off]
|
||
By default, super page will be supported if Intel IOMMU
|
||
has the capability. With this option, super page will
|
||
not be supported.
|
||
sm_on
|
||
Enable the Intel IOMMU scalable mode if the hardware
|
||
advertises that it has support for the scalable mode
|
||
translation.
|
||
sm_off
|
||
Disallow use of the Intel IOMMU scalable mode.
|
||
tboot_noforce [Default Off]
|
||
Do not force the Intel IOMMU enabled under tboot.
|
||
By default, tboot will force Intel IOMMU on, which
|
||
could harm performance of some high-throughput
|
||
devices like 40GBit network cards, even if identity
|
||
mapping is enabled.
|
||
Note that using this option lowers the security
|
||
provided by tboot because it makes the system
|
||
vulnerable to DMA attacks.
|
||
|
||
intel_idle.max_cstate= [KNL,HW,ACPI,X86]
|
||
0 disables intel_idle and fall back on acpi_idle.
|
||
1 to 9 specify maximum depth of C-state.
|
||
|
||
intel_pstate= [X86,EARLY]
|
||
disable
|
||
Do not enable intel_pstate as the default
|
||
scaling driver for the supported processors
|
||
active
|
||
Use intel_pstate driver to bypass the scaling
|
||
governors layer of cpufreq and provides it own
|
||
algorithms for p-state selection. There are two
|
||
P-state selection algorithms provided by
|
||
intel_pstate in the active mode: powersave and
|
||
performance. The way they both operate depends
|
||
on whether or not the hardware managed P-states
|
||
(HWP) feature has been enabled in the processor
|
||
and possibly on the processor model.
|
||
passive
|
||
Use intel_pstate as a scaling driver, but configure it
|
||
to work with generic cpufreq governors (instead of
|
||
enabling its internal governor). This mode cannot be
|
||
used along with the hardware-managed P-states (HWP)
|
||
feature.
|
||
force
|
||
Enable intel_pstate on systems that prohibit it by default
|
||
in favor of acpi-cpufreq. Forcing the intel_pstate driver
|
||
instead of acpi-cpufreq may disable platform features, such
|
||
as thermal controls and power capping, that rely on ACPI
|
||
P-States information being indicated to OSPM and therefore
|
||
should be used with caution. This option does not work with
|
||
processors that aren't supported by the intel_pstate driver
|
||
or on platforms that use pcc-cpufreq instead of acpi-cpufreq.
|
||
no_hwp
|
||
Do not enable hardware P state control (HWP)
|
||
if available.
|
||
hwp_only
|
||
Only load intel_pstate on systems which support
|
||
hardware P state control (HWP) if available.
|
||
support_acpi_ppc
|
||
Enforce ACPI _PPC performance limits. If the Fixed ACPI
|
||
Description Table, specifies preferred power management
|
||
profile as "Enterprise Server" or "Performance Server",
|
||
then this feature is turned on by default.
|
||
per_cpu_perf_limits
|
||
Allow per-logical-CPU P-State performance control limits using
|
||
cpufreq sysfs interface
|
||
|
||
intremap= [X86-64,Intel-IOMMU,EARLY]
|
||
on enable Interrupt Remapping (default)
|
||
off disable Interrupt Remapping
|
||
nosid disable Source ID checking
|
||
no_x2apic_optout
|
||
BIOS x2APIC opt-out request will be ignored
|
||
nopost disable Interrupt Posting
|
||
posted_msi
|
||
enable MSIs delivered as posted interrupts
|
||
|
||
iomem= Disable strict checking of access to MMIO memory
|
||
strict regions from userspace.
|
||
relaxed
|
||
|
||
iommu= [X86,EARLY]
|
||
off
|
||
force
|
||
noforce
|
||
biomerge
|
||
panic
|
||
nopanic
|
||
merge
|
||
nomerge
|
||
soft
|
||
pt [X86]
|
||
nopt [X86]
|
||
nobypass [PPC/POWERNV]
|
||
Disable IOMMU bypass, using IOMMU for PCI devices.
|
||
|
||
iommu.forcedac= [ARM64,X86,EARLY] Control IOVA allocation for PCI devices.
|
||
Format: { "0" | "1" }
|
||
0 - Try to allocate a 32-bit DMA address first, before
|
||
falling back to the full range if needed.
|
||
1 - Allocate directly from the full usable range,
|
||
forcing Dual Address Cycle for PCI cards supporting
|
||
greater than 32-bit addressing.
|
||
|
||
iommu.strict= [ARM64,X86,S390,EARLY] Configure TLB invalidation behaviour
|
||
Format: { "0" | "1" }
|
||
0 - Lazy mode.
|
||
Request that DMA unmap operations use deferred
|
||
invalidation of hardware TLBs, for increased
|
||
throughput at the cost of reduced device isolation.
|
||
Will fall back to strict mode if not supported by
|
||
the relevant IOMMU driver.
|
||
1 - Strict mode.
|
||
DMA unmap operations invalidate IOMMU hardware TLBs
|
||
synchronously.
|
||
unset - Use value of CONFIG_IOMMU_DEFAULT_DMA_{LAZY,STRICT}.
|
||
Note: on x86, strict mode specified via one of the
|
||
legacy driver-specific options takes precedence.
|
||
|
||
iommu.passthrough=
|
||
[ARM64,X86,EARLY] Configure DMA to bypass the IOMMU by default.
|
||
Format: { "0" | "1" }
|
||
0 - Use IOMMU translation for DMA.
|
||
1 - Bypass the IOMMU for DMA.
|
||
unset - Use value of CONFIG_IOMMU_DEFAULT_PASSTHROUGH.
|
||
|
||
io7= [HW] IO7 for Marvel-based Alpha systems
|
||
See comment before marvel_specify_io7 in
|
||
arch/alpha/kernel/core_marvel.c.
|
||
|
||
io_delay= [X86,EARLY] I/O delay method
|
||
0x80
|
||
Standard port 0x80 based delay
|
||
0xed
|
||
Alternate port 0xed based delay (needed on some systems)
|
||
udelay
|
||
Simple two microseconds delay
|
||
none
|
||
No delay
|
||
|
||
ip= [IP_PNP]
|
||
See Documentation/admin-guide/nfs/nfsroot.rst.
|
||
|
||
ipcmni_extend [KNL,EARLY] Extend the maximum number of unique System V
|
||
IPC identifiers from 32,768 to 16,777,216.
|
||
|
||
ipe.enforce= [IPE]
|
||
Format: <bool>
|
||
Determine whether IPE starts in permissive (0) or
|
||
enforce (1) mode. The default is enforce.
|
||
|
||
ipe.success_audit=
|
||
[IPE]
|
||
Format: <bool>
|
||
Start IPE with success auditing enabled, emitting
|
||
an audit event when a binary is allowed. The default
|
||
is 0.
|
||
|
||
irqaffinity= [SMP] Set the default irq affinity mask
|
||
The argument is a cpu list, as described above.
|
||
|
||
irqchip.gicv2_force_probe=
|
||
[ARM,ARM64,EARLY]
|
||
Format: <bool>
|
||
Force the kernel to look for the second 4kB page
|
||
of a GICv2 controller even if the memory range
|
||
exposed by the device tree is too small.
|
||
|
||
irqchip.gicv3_nolpi=
|
||
[ARM,ARM64,EARLY]
|
||
Force the kernel to ignore the availability of
|
||
LPIs (and by consequence ITSs). Intended for system
|
||
that use the kernel as a bootloader, and thus want
|
||
to let secondary kernels in charge of setting up
|
||
LPIs.
|
||
|
||
irqchip.gicv3_pseudo_nmi= [ARM64,EARLY]
|
||
Enables support for pseudo-NMIs in the kernel. This
|
||
requires the kernel to be built with
|
||
CONFIG_ARM64_PSEUDO_NMI.
|
||
|
||
irqfixup [HW]
|
||
When an interrupt is not handled search all handlers
|
||
for it. Intended to get systems with badly broken
|
||
firmware running.
|
||
|
||
irqpoll [HW]
|
||
When an interrupt is not handled search all handlers
|
||
for it. Also check all handlers each timer
|
||
interrupt. Intended to get systems with badly broken
|
||
firmware running.
|
||
|
||
isapnp= [ISAPNP]
|
||
Format: <RDP>,<reset>,<pci_scan>,<verbosity>
|
||
|
||
isolcpus= [KNL,SMP,ISOL] Isolate a given set of CPUs from disturbance.
|
||
[Deprecated - use cpusets instead]
|
||
Format: [flag-list,]<cpu-list>
|
||
|
||
Specify one or more CPUs to isolate from disturbances
|
||
specified in the flag list (default: domain):
|
||
|
||
nohz
|
||
Disable the tick when a single task runs.
|
||
|
||
A residual 1Hz tick is offloaded to workqueues, which you
|
||
need to affine to housekeeping through the global
|
||
workqueue's affinity configured via the
|
||
/sys/devices/virtual/workqueue/cpumask sysfs file, or
|
||
by using the 'domain' flag described below.
|
||
|
||
NOTE: by default the global workqueue runs on all CPUs,
|
||
so to protect individual CPUs the 'cpumask' file has to
|
||
be configured manually after bootup.
|
||
|
||
domain
|
||
Isolate from the general SMP balancing and scheduling
|
||
algorithms. Note that performing domain isolation this way
|
||
is irreversible: it's not possible to bring back a CPU to
|
||
the domains once isolated through isolcpus. It's strongly
|
||
advised to use cpusets instead to disable scheduler load
|
||
balancing through the "cpuset.sched_load_balance" file.
|
||
It offers a much more flexible interface where CPUs can
|
||
move in and out of an isolated set anytime.
|
||
|
||
You can move a process onto or off an "isolated" CPU via
|
||
the CPU affinity syscalls or cpuset.
|
||
<cpu number> begins at 0 and the maximum value is
|
||
"number of CPUs in system - 1".
|
||
|
||
managed_irq
|
||
|
||
Isolate from being targeted by managed interrupts
|
||
which have an interrupt mask containing isolated
|
||
CPUs. The affinity of managed interrupts is
|
||
handled by the kernel and cannot be changed via
|
||
the /proc/irq/* interfaces.
|
||
|
||
This isolation is best effort and only effective
|
||
if the automatically assigned interrupt mask of a
|
||
device queue contains isolated and housekeeping
|
||
CPUs. If housekeeping CPUs are online then such
|
||
interrupts are directed to the housekeeping CPU
|
||
so that IO submitted on the housekeeping CPU
|
||
cannot disturb the isolated CPU.
|
||
|
||
If a queue's affinity mask contains only isolated
|
||
CPUs then this parameter has no effect on the
|
||
interrupt routing decision, though interrupts are
|
||
only delivered when tasks running on those
|
||
isolated CPUs submit IO. IO submitted on
|
||
housekeeping CPUs has no influence on those
|
||
queues.
|
||
|
||
The format of <cpu-list> is described above.
|
||
|
||
iucv= [HW,NET]
|
||
|
||
ivrs_ioapic [HW,X86-64]
|
||
Provide an override to the IOAPIC-ID<->DEVICE-ID
|
||
mapping provided in the IVRS ACPI table.
|
||
By default, PCI segment is 0, and can be omitted.
|
||
|
||
For example, to map IOAPIC-ID decimal 10 to
|
||
PCI segment 0x1 and PCI device 00:14.0,
|
||
write the parameter as:
|
||
ivrs_ioapic=10@0001:00:14.0
|
||
|
||
Deprecated formats:
|
||
* To map IOAPIC-ID decimal 10 to PCI device 00:14.0
|
||
write the parameter as:
|
||
ivrs_ioapic[10]=00:14.0
|
||
* To map IOAPIC-ID decimal 10 to PCI segment 0x1 and
|
||
PCI device 00:14.0 write the parameter as:
|
||
ivrs_ioapic[10]=0001:00:14.0
|
||
|
||
ivrs_hpet [HW,X86-64]
|
||
Provide an override to the HPET-ID<->DEVICE-ID
|
||
mapping provided in the IVRS ACPI table.
|
||
By default, PCI segment is 0, and can be omitted.
|
||
|
||
For example, to map HPET-ID decimal 10 to
|
||
PCI segment 0x1 and PCI device 00:14.0,
|
||
write the parameter as:
|
||
ivrs_hpet=10@0001:00:14.0
|
||
|
||
Deprecated formats:
|
||
* To map HPET-ID decimal 0 to PCI device 00:14.0
|
||
write the parameter as:
|
||
ivrs_hpet[0]=00:14.0
|
||
* To map HPET-ID decimal 10 to PCI segment 0x1 and
|
||
PCI device 00:14.0 write the parameter as:
|
||
ivrs_ioapic[10]=0001:00:14.0
|
||
|
||
ivrs_acpihid [HW,X86-64]
|
||
Provide an override to the ACPI-HID:UID<->DEVICE-ID
|
||
mapping provided in the IVRS ACPI table.
|
||
By default, PCI segment is 0, and can be omitted.
|
||
|
||
For example, to map UART-HID:UID AMD0020:0 to
|
||
PCI segment 0x1 and PCI device ID 00:14.5,
|
||
write the parameter as:
|
||
ivrs_acpihid=AMD0020:0@0001:00:14.5
|
||
|
||
Deprecated formats:
|
||
* To map UART-HID:UID AMD0020:0 to PCI segment is 0,
|
||
PCI device ID 00:14.5, write the parameter as:
|
||
ivrs_acpihid[00:14.5]=AMD0020:0
|
||
* To map UART-HID:UID AMD0020:0 to PCI segment 0x1 and
|
||
PCI device ID 00:14.5, write the parameter as:
|
||
ivrs_acpihid[0001:00:14.5]=AMD0020:0
|
||
|
||
js= [HW,JOY] Analog joystick
|
||
See Documentation/input/joydev/joystick.rst.
|
||
|
||
kasan_multi_shot
|
||
[KNL] Enforce KASAN (Kernel Address Sanitizer) to print
|
||
report on every invalid memory access. Without this
|
||
parameter KASAN will print report only for the first
|
||
invalid access.
|
||
|
||
keep_bootcon [KNL,EARLY]
|
||
Do not unregister boot console at start. This is only
|
||
useful for debugging when something happens in the window
|
||
between unregistering the boot console and initializing
|
||
the real console.
|
||
|
||
keepinitrd [HW,ARM] See retain_initrd.
|
||
|
||
kernelcore= [KNL,X86,PPC,EARLY]
|
||
Format: nn[KMGTPE] | nn% | "mirror"
|
||
This parameter specifies the amount of memory usable by
|
||
the kernel for non-movable allocations. The requested
|
||
amount is spread evenly throughout all nodes in the
|
||
system as ZONE_NORMAL. The remaining memory is used for
|
||
movable memory in its own zone, ZONE_MOVABLE. In the
|
||
event, a node is too small to have both ZONE_NORMAL and
|
||
ZONE_MOVABLE, kernelcore memory will take priority and
|
||
other nodes will have a larger ZONE_MOVABLE.
|
||
|
||
ZONE_MOVABLE is used for the allocation of pages that
|
||
may be reclaimed or moved by the page migration
|
||
subsystem. Note that allocations like PTEs-from-HighMem
|
||
still use the HighMem zone if it exists, and the Normal
|
||
zone if it does not.
|
||
|
||
It is possible to specify the exact amount of memory in
|
||
the form of "nn[KMGTPE]", a percentage of total system
|
||
memory in the form of "nn%", or "mirror". If "mirror"
|
||
option is specified, mirrored (reliable) memory is used
|
||
for non-movable allocations and remaining memory is used
|
||
for Movable pages. "nn[KMGTPE]", "nn%", and "mirror"
|
||
are exclusive, so you cannot specify multiple forms.
|
||
|
||
kgdbdbgp= [KGDB,HW,EARLY] kgdb over EHCI usb debug port.
|
||
Format: <Controller#>[,poll interval]
|
||
The controller # is the number of the ehci usb debug
|
||
port as it is probed via PCI. The poll interval is
|
||
optional and is the number seconds in between
|
||
each poll cycle to the debug port in case you need
|
||
the functionality for interrupting the kernel with
|
||
gdb or control-c on the dbgp connection. When
|
||
not using this parameter you use sysrq-g to break into
|
||
the kernel debugger.
|
||
|
||
kgdboc= [KGDB,HW] kgdb over consoles.
|
||
Requires a tty driver that supports console polling,
|
||
or a supported polling keyboard driver (non-usb).
|
||
Serial only format: <serial_device>[,baud]
|
||
keyboard only format: kbd
|
||
keyboard and serial format: kbd,<serial_device>[,baud]
|
||
Optional Kernel mode setting:
|
||
kms, kbd format: kms,kbd
|
||
kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
|
||
|
||
kgdboc_earlycon= [KGDB,HW,EARLY]
|
||
If the boot console provides the ability to read
|
||
characters and can work in polling mode, you can use
|
||
this parameter to tell kgdb to use it as a backend
|
||
until the normal console is registered. Intended to
|
||
be used together with the kgdboc parameter which
|
||
specifies the normal console to transition to.
|
||
|
||
The name of the early console should be specified
|
||
as the value of this parameter. Note that the name of
|
||
the early console might be different than the tty
|
||
name passed to kgdboc. It's OK to leave the value
|
||
blank and the first boot console that implements
|
||
read() will be picked.
|
||
|
||
kgdbwait [KGDB,EARLY] Stop kernel execution and enter the
|
||
kernel debugger at the earliest opportunity.
|
||
|
||
kmac= [MIPS] Korina ethernet MAC address.
|
||
Configure the RouterBoard 532 series on-chip
|
||
Ethernet adapter MAC address.
|
||
|
||
kmemleak= [KNL,EARLY] Boot-time kmemleak enable/disable
|
||
Valid arguments: on, off
|
||
Default: on
|
||
Built with CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y,
|
||
the default is off.
|
||
|
||
kprobe_event=[probe-list]
|
||
[FTRACE] Add kprobe events and enable at boot time.
|
||
The probe-list is a semicolon delimited list of probe
|
||
definitions. Each definition is same as kprobe_events
|
||
interface, but the parameters are comma delimited.
|
||
For example, to add a kprobe event on vfs_read with
|
||
arg1 and arg2, add to the command line;
|
||
|
||
kprobe_event=p,vfs_read,$arg1,$arg2
|
||
|
||
See also Documentation/trace/kprobetrace.rst "Kernel
|
||
Boot Parameter" section.
|
||
|
||
kpti= [ARM64,EARLY] Control page table isolation of
|
||
user and kernel address spaces.
|
||
Default: enabled on cores which need mitigation.
|
||
0: force disabled
|
||
1: force enabled
|
||
|
||
kunit.enable= [KUNIT] Enable executing KUnit tests. Requires
|
||
CONFIG_KUNIT to be set to be fully enabled. The
|
||
default value can be overridden via
|
||
KUNIT_DEFAULT_ENABLED.
|
||
Default is 1 (enabled)
|
||
|
||
kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
|
||
Default is 0 (don't ignore, but inject #GP)
|
||
|
||
kvm.eager_page_split=
|
||
[KVM,X86] Controls whether or not KVM will try to
|
||
proactively split all huge pages during dirty logging.
|
||
Eager page splitting reduces interruptions to vCPU
|
||
execution by eliminating the write-protection faults
|
||
and MMU lock contention that would otherwise be
|
||
required to split huge pages lazily.
|
||
|
||
VM workloads that rarely perform writes or that write
|
||
only to a small region of VM memory may benefit from
|
||
disabling eager page splitting to allow huge pages to
|
||
still be used for reads.
|
||
|
||
The behavior of eager page splitting depends on whether
|
||
KVM_DIRTY_LOG_INITIALLY_SET is enabled or disabled. If
|
||
disabled, all huge pages in a memslot will be eagerly
|
||
split when dirty logging is enabled on that memslot. If
|
||
enabled, eager page splitting will be performed during
|
||
the KVM_CLEAR_DIRTY ioctl, and only for the pages being
|
||
cleared.
|
||
|
||
Eager page splitting is only supported when kvm.tdp_mmu=Y.
|
||
|
||
Default is Y (on).
|
||
|
||
kvm.enable_virt_at_load=[KVM,ARM64,LOONGARCH,MIPS,RISCV,X86]
|
||
If enabled, KVM will enable virtualization in hardware
|
||
when KVM is loaded, and disable virtualization when KVM
|
||
is unloaded (if KVM is built as a module).
|
||
|
||
If disabled, KVM will dynamically enable and disable
|
||
virtualization on-demand when creating and destroying
|
||
VMs, i.e. on the 0=>1 and 1=>0 transitions of the
|
||
number of VMs.
|
||
|
||
Enabling virtualization at module lode avoids potential
|
||
latency for creation of the 0=>1 VM, as KVM serializes
|
||
virtualization enabling across all online CPUs. The
|
||
"cost" of enabling virtualization when KVM is loaded,
|
||
is that doing so may interfere with using out-of-tree
|
||
hypervisors that want to "own" virtualization hardware.
|
||
|
||
kvm.enable_vmware_backdoor=[KVM] Support VMware backdoor PV interface.
|
||
Default is false (don't support).
|
||
|
||
kvm.nx_huge_pages=
|
||
[KVM] Controls the software workaround for the
|
||
X86_BUG_ITLB_MULTIHIT bug.
|
||
force : Always deploy workaround.
|
||
off : Never deploy workaround.
|
||
auto : Deploy workaround based on the presence of
|
||
X86_BUG_ITLB_MULTIHIT.
|
||
|
||
Default is 'auto'.
|
||
|
||
If the software workaround is enabled for the host,
|
||
guests do need not to enable it for nested guests.
|
||
|
||
kvm.nx_huge_pages_recovery_ratio=
|
||
[KVM] Controls how many 4KiB pages are periodically zapped
|
||
back to huge pages. 0 disables the recovery, otherwise if
|
||
the value is N KVM will zap 1/Nth of the 4KiB pages every
|
||
period (see below). The default is 60.
|
||
|
||
kvm.nx_huge_pages_recovery_period_ms=
|
||
[KVM] Controls the time period at which KVM zaps 4KiB pages
|
||
back to huge pages. If the value is a non-zero N, KVM will
|
||
zap a portion (see ratio above) of the pages every N msecs.
|
||
If the value is 0 (the default), KVM will pick a period based
|
||
on the ratio, such that a page is zapped after 1 hour on average.
|
||
|
||
kvm-amd.nested= [KVM,AMD] Control nested virtualization feature in
|
||
KVM/SVM. Default is 1 (enabled).
|
||
|
||
kvm-amd.npt= [KVM,AMD] Control KVM's use of Nested Page Tables,
|
||
a.k.a. Two-Dimensional Page Tables. Default is 1
|
||
(enabled). Disable by KVM if hardware lacks support
|
||
for NPT.
|
||
|
||
kvm-arm.mode=
|
||
[KVM,ARM,EARLY] Select one of KVM/arm64's modes of
|
||
operation.
|
||
|
||
none: Forcefully disable KVM.
|
||
|
||
nvhe: Standard nVHE-based mode, without support for
|
||
protected guests.
|
||
|
||
protected: nVHE-based mode with support for guests whose
|
||
state is kept private from the host.
|
||
|
||
nested: VHE-based mode with support for nested
|
||
virtualization. Requires at least ARMv8.3
|
||
hardware.
|
||
|
||
Defaults to VHE/nVHE based on hardware support. Setting
|
||
mode to "protected" will disable kexec and hibernation
|
||
for the host. "nested" is experimental and should be
|
||
used with extreme caution.
|
||
|
||
kvm-arm.vgic_v3_group0_trap=
|
||
[KVM,ARM,EARLY] Trap guest accesses to GICv3 group-0
|
||
system registers
|
||
|
||
kvm-arm.vgic_v3_group1_trap=
|
||
[KVM,ARM,EARLY] Trap guest accesses to GICv3 group-1
|
||
system registers
|
||
|
||
kvm-arm.vgic_v3_common_trap=
|
||
[KVM,ARM,EARLY] Trap guest accesses to GICv3 common
|
||
system registers
|
||
|
||
kvm-arm.vgic_v4_enable=
|
||
[KVM,ARM,EARLY] Allow use of GICv4 for direct
|
||
injection of LPIs.
|
||
|
||
kvm-arm.wfe_trap_policy=
|
||
[KVM,ARM] Control when to set WFE instruction trap for
|
||
KVM VMs. Traps are allowed but not guaranteed by the
|
||
CPU architecture.
|
||
|
||
trap: set WFE instruction trap
|
||
|
||
notrap: clear WFE instruction trap
|
||
|
||
kvm-arm.wfi_trap_policy=
|
||
[KVM,ARM] Control when to set WFI instruction trap for
|
||
KVM VMs. Traps are allowed but not guaranteed by the
|
||
CPU architecture.
|
||
|
||
trap: set WFI instruction trap
|
||
|
||
notrap: clear WFI instruction trap
|
||
|
||
kvm_cma_resv_ratio=n [PPC,EARLY]
|
||
Reserves given percentage from system memory area for
|
||
contiguous memory allocation for KVM hash pagetable
|
||
allocation.
|
||
By default it reserves 5% of total system memory.
|
||
Format: <integer>
|
||
Default: 5
|
||
|
||
kvm-intel.ept= [KVM,Intel] Control KVM's use of Extended Page Tables,
|
||
a.k.a. Two-Dimensional Page Tables. Default is 1
|
||
(enabled). Disable by KVM if hardware lacks support
|
||
for EPT.
|
||
|
||
kvm-intel.emulate_invalid_guest_state=
|
||
[KVM,Intel] Control whether to emulate invalid guest
|
||
state. Ignored if kvm-intel.enable_unrestricted_guest=1,
|
||
as guest state is never invalid for unrestricted
|
||
guests. This param doesn't apply to nested guests (L2),
|
||
as KVM never emulates invalid L2 guest state.
|
||
Default is 1 (enabled).
|
||
|
||
kvm-intel.flexpriority=
|
||
[KVM,Intel] Control KVM's use of FlexPriority feature
|
||
(TPR shadow). Default is 1 (enabled). Disable by KVM if
|
||
hardware lacks support for it.
|
||
|
||
kvm-intel.nested=
|
||
[KVM,Intel] Control nested virtualization feature in
|
||
KVM/VMX. Default is 1 (enabled).
|
||
|
||
kvm-intel.unrestricted_guest=
|
||
[KVM,Intel] Control KVM's use of unrestricted guest
|
||
feature (virtualized real and unpaged mode). Default
|
||
is 1 (enabled). Disable by KVM if EPT is disabled or
|
||
hardware lacks support for it.
|
||
|
||
kvm-intel.vmentry_l1d_flush=[KVM,Intel] Mitigation for L1 Terminal Fault
|
||
CVE-2018-3620.
|
||
|
||
Valid arguments: never, cond, always
|
||
|
||
always: L1D cache flush on every VMENTER.
|
||
cond: Flush L1D on VMENTER only when the code between
|
||
VMEXIT and VMENTER can leak host memory.
|
||
never: Disables the mitigation
|
||
|
||
Default is cond (do L1 cache flush in specific instances)
|
||
|
||
kvm-intel.vpid= [KVM,Intel] Control KVM's use of Virtual Processor
|
||
Identification feature (tagged TLBs). Default is 1
|
||
(enabled). Disable by KVM if hardware lacks support
|
||
for it.
|
||
|
||
l1d_flush= [X86,INTEL,EARLY]
|
||
Control mitigation for L1D based snooping vulnerability.
|
||
|
||
Certain CPUs are vulnerable to an exploit against CPU
|
||
internal buffers which can forward information to a
|
||
disclosure gadget under certain conditions.
|
||
|
||
In vulnerable processors, the speculatively
|
||
forwarded data can be used in a cache side channel
|
||
attack, to access data to which the attacker does
|
||
not have direct access.
|
||
|
||
This parameter controls the mitigation. The
|
||
options are:
|
||
|
||
on - enable the interface for the mitigation
|
||
|
||
l1tf= [X86,EARLY] Control mitigation of the L1TF vulnerability on
|
||
affected CPUs
|
||
|
||
The kernel PTE inversion protection is unconditionally
|
||
enabled and cannot be disabled.
|
||
|
||
full
|
||
Provides all available mitigations for the
|
||
L1TF vulnerability. Disables SMT and
|
||
enables all mitigations in the
|
||
hypervisors, i.e. unconditional L1D flush.
|
||
|
||
SMT control and L1D flush control via the
|
||
sysfs interface is still possible after
|
||
boot. Hypervisors will issue a warning
|
||
when the first VM is started in a
|
||
potentially insecure configuration,
|
||
i.e. SMT enabled or L1D flush disabled.
|
||
|
||
full,force
|
||
Same as 'full', but disables SMT and L1D
|
||
flush runtime control. Implies the
|
||
'nosmt=force' command line option.
|
||
(i.e. sysfs control of SMT is disabled.)
|
||
|
||
flush
|
||
Leaves SMT enabled and enables the default
|
||
hypervisor mitigation, i.e. conditional
|
||
L1D flush.
|
||
|
||
SMT control and L1D flush control via the
|
||
sysfs interface is still possible after
|
||
boot. Hypervisors will issue a warning
|
||
when the first VM is started in a
|
||
potentially insecure configuration,
|
||
i.e. SMT enabled or L1D flush disabled.
|
||
|
||
flush,nosmt
|
||
|
||
Disables SMT and enables the default
|
||
hypervisor mitigation.
|
||
|
||
SMT control and L1D flush control via the
|
||
sysfs interface is still possible after
|
||
boot. Hypervisors will issue a warning
|
||
when the first VM is started in a
|
||
potentially insecure configuration,
|
||
i.e. SMT enabled or L1D flush disabled.
|
||
|
||
flush,nowarn
|
||
Same as 'flush', but hypervisors will not
|
||
warn when a VM is started in a potentially
|
||
insecure configuration.
|
||
|
||
off
|
||
Disables hypervisor mitigations and doesn't
|
||
emit any warnings.
|
||
It also drops the swap size and available
|
||
RAM limit restriction on both hypervisor and
|
||
bare metal.
|
||
|
||
Default is 'flush'.
|
||
|
||
For details see: Documentation/admin-guide/hw-vuln/l1tf.rst
|
||
|
||
l2cr= [PPC]
|
||
|
||
l3cr= [PPC]
|
||
|
||
lapic [X86-32,APIC,EARLY] Enable the local APIC even if BIOS
|
||
disabled it.
|
||
|
||
lapic= [X86,APIC] Do not use TSC deadline
|
||
value for LAPIC timer one-shot implementation. Default
|
||
back to the programmable timer unit in the LAPIC.
|
||
Format: notscdeadline
|
||
|
||
lapic_timer_c2_ok [X86,APIC,EARLY] trust the local apic timer
|
||
in C2 power state.
|
||
|
||
libata.dma= [LIBATA] DMA control
|
||
libata.dma=0 Disable all PATA and SATA DMA
|
||
libata.dma=1 PATA and SATA Disk DMA only
|
||
libata.dma=2 ATAPI (CDROM) DMA only
|
||
libata.dma=4 Compact Flash DMA only
|
||
Combinations also work, so libata.dma=3 enables DMA
|
||
for disks and CDROMs, but not CFs.
|
||
|
||
libata.ignore_hpa= [LIBATA] Ignore HPA limit
|
||
libata.ignore_hpa=0 keep BIOS limits (default)
|
||
libata.ignore_hpa=1 ignore limits, using full disk
|
||
|
||
libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
|
||
when set.
|
||
Format: <int>
|
||
|
||
libata.force= [LIBATA] Force configurations. The format is a comma-
|
||
separated list of "[ID:]VAL" where ID is PORT[.DEVICE].
|
||
PORT and DEVICE are decimal numbers matching port, link
|
||
or device. Basically, it matches the ATA ID string
|
||
printed on console by libata. If the whole ID part is
|
||
omitted, the last PORT and DEVICE values are used. If
|
||
ID hasn't been specified yet, the configuration applies
|
||
to all ports, links and devices.
|
||
|
||
If only DEVICE is omitted, the parameter applies to
|
||
the port and all links and devices behind it. DEVICE
|
||
number of 0 either selects the first device or the
|
||
first fan-out link behind PMP device. It does not
|
||
select the host link. DEVICE number of 15 selects the
|
||
host link and device attached to it.
|
||
|
||
The VAL specifies the configuration to force. As long
|
||
as there is no ambiguity, shortcut notation is allowed.
|
||
For example, both 1.5 and 1.5G would work for 1.5Gbps.
|
||
The following configurations can be forced.
|
||
|
||
* Cable type: 40c, 80c, short40c, unk, ign or sata.
|
||
Any ID with matching PORT is used.
|
||
|
||
* SATA link speed limit: 1.5Gbps or 3.0Gbps.
|
||
|
||
* Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
|
||
udma[/][16,25,33,44,66,100,133] notation is also
|
||
allowed.
|
||
|
||
* nohrst, nosrst, norst: suppress hard, soft and both
|
||
resets.
|
||
|
||
* rstonce: only attempt one reset during hot-unplug
|
||
link recovery.
|
||
|
||
* [no]dbdelay: Enable or disable the extra 200ms delay
|
||
before debouncing a link PHY and device presence
|
||
detection.
|
||
|
||
* [no]ncq: Turn on or off NCQ.
|
||
|
||
* [no]ncqtrim: Enable or disable queued DSM TRIM.
|
||
|
||
* [no]ncqati: Enable or disable NCQ trim on ATI chipset.
|
||
|
||
* [no]trim: Enable or disable (unqueued) TRIM.
|
||
|
||
* trim_zero: Indicate that TRIM command zeroes data.
|
||
|
||
* max_trim_128m: Set 128M maximum trim size limit.
|
||
|
||
* [no]dma: Turn on or off DMA transfers.
|
||
|
||
* atapi_dmadir: Enable ATAPI DMADIR bridge support.
|
||
|
||
* atapi_mod16_dma: Enable the use of ATAPI DMA for
|
||
commands that are not a multiple of 16 bytes.
|
||
|
||
* [no]dmalog: Enable or disable the use of the
|
||
READ LOG DMA EXT command to access logs.
|
||
|
||
* [no]iddevlog: Enable or disable access to the
|
||
identify device data log.
|
||
|
||
* [no]logdir: Enable or disable access to the general
|
||
purpose log directory.
|
||
|
||
* max_sec_128: Set transfer size limit to 128 sectors.
|
||
|
||
* max_sec_1024: Set or clear transfer size limit to
|
||
1024 sectors.
|
||
|
||
* max_sec_lba48: Set or clear transfer size limit to
|
||
65535 sectors.
|
||
|
||
* [no]lpm: Enable or disable link power management.
|
||
|
||
* [no]setxfer: Indicate if transfer speed mode setting
|
||
should be skipped.
|
||
|
||
* [no]fua: Disable or enable FUA (Force Unit Access)
|
||
support for devices supporting this feature.
|
||
|
||
* dump_id: Dump IDENTIFY data.
|
||
|
||
* disable: Disable this device.
|
||
|
||
If there are multiple matching configurations changing
|
||
the same attribute, the last one is used.
|
||
|
||
load_ramdisk= [RAM] [Deprecated]
|
||
|
||
lockd.nlm_grace_period=P [NFS] Assign grace period.
|
||
Format: <integer>
|
||
|
||
lockd.nlm_tcpport=N [NFS] Assign TCP port.
|
||
Format: <integer>
|
||
|
||
lockd.nlm_timeout=T [NFS] Assign timeout value.
|
||
Format: <integer>
|
||
|
||
lockd.nlm_udpport=M [NFS] Assign UDP port.
|
||
Format: <integer>
|
||
|
||
lockdown= [SECURITY,EARLY]
|
||
{ integrity | confidentiality }
|
||
Enable the kernel lockdown feature. If set to
|
||
integrity, kernel features that allow userland to
|
||
modify the running kernel are disabled. If set to
|
||
confidentiality, kernel features that allow userland
|
||
to extract confidential information from the kernel
|
||
are also disabled.
|
||
|
||
locktorture.acq_writer_lim= [KNL]
|
||
Set the time limit in jiffies for a lock
|
||
acquisition. Acquisitions exceeding this limit
|
||
will result in a splat once they do complete.
|
||
|
||
locktorture.bind_readers= [KNL]
|
||
Specify the list of CPUs to which the readers are
|
||
to be bound.
|
||
|
||
locktorture.bind_writers= [KNL]
|
||
Specify the list of CPUs to which the writers are
|
||
to be bound.
|
||
|
||
locktorture.call_rcu_chains= [KNL]
|
||
Specify the number of self-propagating call_rcu()
|
||
chains to set up. These are used to ensure that
|
||
there is a high probability of an RCU grace period
|
||
in progress at any given time. Defaults to 0,
|
||
which disables these call_rcu() chains.
|
||
|
||
locktorture.long_hold= [KNL]
|
||
Specify the duration in milliseconds for the
|
||
occasional long-duration lock hold time. Defaults
|
||
to 100 milliseconds. Select 0 to disable.
|
||
|
||
locktorture.nested_locks= [KNL]
|
||
Specify the maximum lock nesting depth that
|
||
locktorture is to exercise, up to a limit of 8
|
||
(MAX_NESTED_LOCKS). Specify zero to disable.
|
||
Note that this parameter is ineffective on types
|
||
of locks that do not support nested acquisition.
|
||
|
||
locktorture.nreaders_stress= [KNL]
|
||
Set the number of locking read-acquisition kthreads.
|
||
Defaults to being automatically set based on the
|
||
number of online CPUs.
|
||
|
||
locktorture.nwriters_stress= [KNL]
|
||
Set the number of locking write-acquisition kthreads.
|
||
|
||
locktorture.onoff_holdoff= [KNL]
|
||
Set time (s) after boot for CPU-hotplug testing.
|
||
|
||
locktorture.onoff_interval= [KNL]
|
||
Set time (s) between CPU-hotplug operations, or
|
||
zero to disable CPU-hotplug testing.
|
||
|
||
locktorture.rt_boost= [KNL]
|
||
Do periodic testing of real-time lock priority
|
||
boosting. Select 0 to disable, 1 to boost
|
||
only rt_mutex, and 2 to boost unconditionally.
|
||
Defaults to 2, which might seem to be an
|
||
odd choice, but which should be harmless for
|
||
non-real-time spinlocks, due to their disabling
|
||
of preemption. Note that non-realtime mutexes
|
||
disable boosting.
|
||
|
||
locktorture.rt_boost_factor= [KNL]
|
||
Number that determines how often and for how
|
||
long priority boosting is exercised. This is
|
||
scaled down by the number of writers, so that the
|
||
number of boosts per unit time remains roughly
|
||
constant as the number of writers increases.
|
||
On the other hand, the duration of each boost
|
||
increases with the number of writers.
|
||
|
||
locktorture.shuffle_interval= [KNL]
|
||
Set task-shuffle interval (jiffies). Shuffling
|
||
tasks allows some CPUs to go into dyntick-idle
|
||
mode during the locktorture test.
|
||
|
||
locktorture.shutdown_secs= [KNL]
|
||
Set time (s) after boot system shutdown. This
|
||
is useful for hands-off automated testing.
|
||
|
||
locktorture.stat_interval= [KNL]
|
||
Time (s) between statistics printk()s.
|
||
|
||
locktorture.stutter= [KNL]
|
||
Time (s) to stutter testing, for example,
|
||
specifying five seconds causes the test to run for
|
||
five seconds, wait for five seconds, and so on.
|
||
This tests the locking primitive's ability to
|
||
transition abruptly to and from idle.
|
||
|
||
locktorture.torture_type= [KNL]
|
||
Specify the locking implementation to test.
|
||
|
||
locktorture.verbose= [KNL]
|
||
Enable additional printk() statements.
|
||
|
||
locktorture.writer_fifo= [KNL]
|
||
Run the write-side locktorture kthreads at
|
||
sched_set_fifo() real-time priority.
|
||
|
||
logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
|
||
Format: <irq>
|
||
|
||
loglevel= [KNL,EARLY]
|
||
All Kernel Messages with a loglevel smaller than the
|
||
console loglevel will be printed to the console. It can
|
||
also be changed with klogd or other programs. The
|
||
loglevels are defined as follows:
|
||
|
||
0 (KERN_EMERG) system is unusable
|
||
1 (KERN_ALERT) action must be taken immediately
|
||
2 (KERN_CRIT) critical conditions
|
||
3 (KERN_ERR) error conditions
|
||
4 (KERN_WARNING) warning conditions
|
||
5 (KERN_NOTICE) normal but significant condition
|
||
6 (KERN_INFO) informational
|
||
7 (KERN_DEBUG) debug-level messages
|
||
|
||
log_buf_len=n[KMG] [KNL,EARLY]
|
||
Sets the size of the printk ring buffer, in bytes.
|
||
n must be a power of two and greater than the
|
||
minimal size. The minimal size is defined by
|
||
LOG_BUF_SHIFT kernel config parameter. There
|
||
is also CONFIG_LOG_CPU_MAX_BUF_SHIFT config
|
||
parameter that allows to increase the default size
|
||
depending on the number of CPUs. See init/Kconfig
|
||
for more details.
|
||
|
||
logo.nologo [FB] Disables display of the built-in Linux logo.
|
||
This may be used to provide more screen space for
|
||
kernel log messages and is useful when debugging
|
||
kernel boot problems.
|
||
|
||
lp=0 [LP] Specify parallel ports to use, e.g,
|
||
lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
|
||
lp=reset first parallel port). 'lp=0' disables the
|
||
lp=auto printer driver. 'lp=reset' (which can be
|
||
specified in addition to the ports) causes
|
||
attached printers to be reset. Using
|
||
lp=port1,port2,... specifies the parallel ports
|
||
to associate lp devices with, starting with
|
||
lp0. A port specification may be 'none' to skip
|
||
that lp device, or a parport name such as
|
||
'parport0'. Specifying 'lp=auto' instead of a
|
||
port specification list means that device IDs
|
||
from each port should be examined, to see if
|
||
an IEEE 1284-compliant printer is attached; if
|
||
so, the driver will manage that printer.
|
||
See also header of drivers/char/lp.c.
|
||
|
||
lpj=n [KNL]
|
||
Sets loops_per_jiffy to given constant, thus avoiding
|
||
time-consuming boot-time autodetection (up to 250 ms per
|
||
CPU). 0 enables autodetection (default). To determine
|
||
the correct value for your kernel, boot with normal
|
||
autodetection and see what value is printed. Note that
|
||
on SMP systems the preset will be applied to all CPUs,
|
||
which is likely to cause problems if your CPUs need
|
||
significantly divergent settings. An incorrect value
|
||
will cause delays in the kernel to be wrong, leading to
|
||
unpredictable I/O errors and other breakage. Although
|
||
unlikely, in the extreme case this might damage your
|
||
hardware.
|
||
|
||
lsm.debug [SECURITY] Enable LSM initialization debugging output.
|
||
|
||
lsm=lsm1,...,lsmN
|
||
[SECURITY] Choose order of LSM initialization. This
|
||
overrides CONFIG_LSM, and the "security=" parameter.
|
||
|
||
machtype= [Loongson] Share the same kernel image file between
|
||
different yeeloong laptops.
|
||
Example: machtype=lemote-yeeloong-2f-7inch
|
||
|
||
maxcpus= [SMP,EARLY] Maximum number of processors that an SMP kernel
|
||
will bring up during bootup. maxcpus=n : n >= 0 limits
|
||
the kernel to bring up 'n' processors. Surely after
|
||
bootup you can bring up the other plugged cpu by executing
|
||
"echo 1 > /sys/devices/system/cpu/cpuX/online". So maxcpus
|
||
only takes effect during system bootup.
|
||
While n=0 is a special case, it is equivalent to "nosmp",
|
||
which also disables the IO APIC.
|
||
|
||
max_loop= [LOOP] The number of loop block devices that get
|
||
(loop.max_loop) unconditionally pre-created at init time. The default
|
||
number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
|
||
of statically allocating a predefined number, loop
|
||
devices can be requested on-demand with the
|
||
/dev/loop-control interface.
|
||
|
||
mce [X86-32] Machine Check Exception
|
||
|
||
mce=option [X86-64] See Documentation/arch/x86/x86_64/boot-options.rst
|
||
|
||
md= [HW] RAID subsystems devices and level
|
||
See Documentation/admin-guide/md.rst.
|
||
|
||
mdacon= [MDA]
|
||
Format: <first>,<last>
|
||
Specifies range of consoles to be captured by the MDA.
|
||
|
||
mds= [X86,INTEL,EARLY]
|
||
Control mitigation for the Micro-architectural Data
|
||
Sampling (MDS) vulnerability.
|
||
|
||
Certain CPUs are vulnerable to an exploit against CPU
|
||
internal buffers which can forward information to a
|
||
disclosure gadget under certain conditions.
|
||
|
||
In vulnerable processors, the speculatively
|
||
forwarded data can be used in a cache side channel
|
||
attack, to access data to which the attacker does
|
||
not have direct access.
|
||
|
||
This parameter controls the MDS mitigation. The
|
||
options are:
|
||
|
||
full - Enable MDS mitigation on vulnerable CPUs
|
||
full,nosmt - Enable MDS mitigation and disable
|
||
SMT on vulnerable CPUs
|
||
off - Unconditionally disable MDS mitigation
|
||
|
||
On TAA-affected machines, mds=off can be prevented by
|
||
an active TAA mitigation as both vulnerabilities are
|
||
mitigated with the same mechanism so in order to disable
|
||
this mitigation, you need to specify tsx_async_abort=off
|
||
too.
|
||
|
||
Not specifying this option is equivalent to
|
||
mds=full.
|
||
|
||
For details see: Documentation/admin-guide/hw-vuln/mds.rst
|
||
|
||
mem=nn[KMG] [HEXAGON,EARLY] Set the memory size.
|
||
Must be specified, otherwise memory size will be 0.
|
||
|
||
mem=nn[KMG] [KNL,BOOT,EARLY] Force usage of a specific amount
|
||
of memory Amount of memory to be used in cases
|
||
as follows:
|
||
|
||
1 for test;
|
||
2 when the kernel is not able to see the whole system memory;
|
||
3 memory that lies after 'mem=' boundary is excluded from
|
||
the hypervisor, then assigned to KVM guests.
|
||
4 to limit the memory available for kdump kernel.
|
||
|
||
[ARC,MICROBLAZE] - the limit applies only to low memory,
|
||
high memory is not affected.
|
||
|
||
[ARM64] - only limits memory covered by the linear
|
||
mapping. The NOMAP regions are not affected.
|
||
|
||
[X86] Work as limiting max address. Use together
|
||
with memmap= to avoid physical address space collisions.
|
||
Without memmap= PCI devices could be placed at addresses
|
||
belonging to unused RAM.
|
||
|
||
Note that this only takes effects during boot time since
|
||
in above case 3, memory may need be hot added after boot
|
||
if system memory of hypervisor is not sufficient.
|
||
|
||
mem=nn[KMG]@ss[KMG]
|
||
[ARM,MIPS,EARLY] - override the memory layout
|
||
reported by firmware.
|
||
Define a memory region of size nn[KMG] starting at
|
||
ss[KMG].
|
||
Multiple different regions can be specified with
|
||
multiple mem= parameters on the command line.
|
||
|
||
mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
|
||
memory.
|
||
|
||
memblock=debug [KNL,EARLY] Enable memblock debug messages.
|
||
|
||
memchunk=nn[KMG]
|
||
[KNL,SH] Allow user to override the default size for
|
||
per-device physically contiguous DMA buffers.
|
||
|
||
memhp_default_state=online/offline/online_kernel/online_movable
|
||
[KNL] Set the initial state for the memory hotplug
|
||
onlining policy. If not specified, the default value is
|
||
set according to the
|
||
CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE kernel config
|
||
option.
|
||
See Documentation/admin-guide/mm/memory-hotplug.rst.
|
||
|
||
memmap=exactmap [KNL,X86,EARLY] Enable setting of an exact
|
||
E820 memory map, as specified by the user.
|
||
Such memmap=exactmap lines can be constructed based on
|
||
BIOS output or other requirements. See the memmap=nn@ss
|
||
option description.
|
||
|
||
memmap=nn[KMG]@ss[KMG]
|
||
[KNL, X86,MIPS,XTENSA,EARLY] Force usage of a specific region of memory.
|
||
Region of memory to be used is from ss to ss+nn.
|
||
If @ss[KMG] is omitted, it is equivalent to mem=nn[KMG],
|
||
which limits max address to nn[KMG].
|
||
Multiple different regions can be specified,
|
||
comma delimited.
|
||
Example:
|
||
memmap=100M@2G,100M#3G,1G!1024G
|
||
|
||
memmap=nn[KMG]#ss[KMG]
|
||
[KNL,ACPI,EARLY] Mark specific memory as ACPI data.
|
||
Region of memory to be marked is from ss to ss+nn.
|
||
|
||
memmap=nn[KMG]$ss[KMG]
|
||
[KNL,ACPI,EARLY] Mark specific memory as reserved.
|
||
Region of memory to be reserved is from ss to ss+nn.
|
||
Example: Exclude memory from 0x18690000-0x1869ffff
|
||
memmap=64K$0x18690000
|
||
or
|
||
memmap=0x10000$0x18690000
|
||
Some bootloaders may need an escape character before '$',
|
||
like Grub2, otherwise '$' and the following number
|
||
will be eaten.
|
||
|
||
memmap=nn[KMG]!ss[KMG,EARLY]
|
||
[KNL,X86] Mark specific memory as protected.
|
||
Region of memory to be used, from ss to ss+nn.
|
||
The memory region may be marked as e820 type 12 (0xc)
|
||
and is NVDIMM or ADR memory.
|
||
|
||
memmap=<size>%<offset>-<oldtype>+<newtype>
|
||
[KNL,ACPI,EARLY] Convert memory within the specified region
|
||
from <oldtype> to <newtype>. If "-<oldtype>" is left
|
||
out, the whole region will be marked as <newtype>,
|
||
even if previously unavailable. If "+<newtype>" is left
|
||
out, matching memory will be removed. Types are
|
||
specified as e820 types, e.g., 1 = RAM, 2 = reserved,
|
||
3 = ACPI, 12 = PRAM.
|
||
|
||
memory_corruption_check=0/1 [X86,EARLY]
|
||
Some BIOSes seem to corrupt the first 64k of
|
||
memory when doing things like suspend/resume.
|
||
Setting this option will scan the memory
|
||
looking for corruption. Enabling this will
|
||
both detect corruption and prevent the kernel
|
||
from using the memory being corrupted.
|
||
However, its intended as a diagnostic tool; if
|
||
repeatable BIOS-originated corruption always
|
||
affects the same memory, you can use memmap=
|
||
to prevent the kernel from using that memory.
|
||
|
||
memory_corruption_check_size=size [X86,EARLY]
|
||
By default it checks for corruption in the low
|
||
64k, making this memory unavailable for normal
|
||
use. Use this parameter to scan for
|
||
corruption in more or less memory.
|
||
|
||
memory_corruption_check_period=seconds [X86,EARLY]
|
||
By default it checks for corruption every 60
|
||
seconds. Use this parameter to check at some
|
||
other rate. 0 disables periodic checking.
|
||
|
||
memory_hotplug.memmap_on_memory
|
||
[KNL,X86,ARM] Boolean flag to enable this feature.
|
||
Format: {on | off (default)}
|
||
When enabled, runtime hotplugged memory will
|
||
allocate its internal metadata (struct pages,
|
||
those vmemmap pages cannot be optimized even
|
||
if hugetlb_free_vmemmap is enabled) from the
|
||
hotadded memory which will allow to hotadd a
|
||
lot of memory without requiring additional
|
||
memory to do so.
|
||
This feature is disabled by default because it
|
||
has some implication on large (e.g. GB)
|
||
allocations in some configurations (e.g. small
|
||
memory blocks).
|
||
The state of the flag can be read in
|
||
/sys/module/memory_hotplug/parameters/memmap_on_memory.
|
||
Note that even when enabled, there are a few cases where
|
||
the feature is not effective.
|
||
|
||
memtest= [KNL,X86,ARM,M68K,PPC,RISCV,EARLY] Enable memtest
|
||
Format: <integer>
|
||
default : 0 <disable>
|
||
Specifies the number of memtest passes to be
|
||
performed. Each pass selects another test
|
||
pattern from a given set of patterns. Memtest
|
||
fills the memory with this pattern, validates
|
||
memory contents and reserves bad memory
|
||
regions that are detected.
|
||
|
||
mem_encrypt= [X86-64] AMD Secure Memory Encryption (SME) control
|
||
Valid arguments: on, off
|
||
Default: off
|
||
mem_encrypt=on: Activate SME
|
||
mem_encrypt=off: Do not activate SME
|
||
|
||
Refer to Documentation/virt/kvm/x86/amd-memory-encryption.rst
|
||
for details on when memory encryption can be activated.
|
||
|
||
mem_sleep_default= [SUSPEND] Default system suspend mode:
|
||
s2idle - Suspend-To-Idle
|
||
shallow - Power-On Suspend or equivalent (if supported)
|
||
deep - Suspend-To-RAM or equivalent (if supported)
|
||
See Documentation/admin-guide/pm/sleep-states.rst.
|
||
|
||
mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
|
||
the BIOS has incorrectly applied a workaround. TinyBIOS
|
||
version 0.98 is known to be affected, 0.99 fixes the
|
||
problem by letting the user disable the workaround.
|
||
|
||
mga= [HW,DRM]
|
||
|
||
microcode.force_minrev= [X86]
|
||
Format: <bool>
|
||
Enable or disable the microcode minimal revision
|
||
enforcement for the runtime microcode loader.
|
||
|
||
mini2440= [ARM,HW,KNL]
|
||
Format:[0..2][b][c][t]
|
||
Default: "0tb"
|
||
MINI2440 configuration specification:
|
||
0 - The attached screen is the 3.5" TFT
|
||
1 - The attached screen is the 7" TFT
|
||
2 - The VGA Shield is attached (1024x768)
|
||
Leaving out the screen size parameter will not load
|
||
the TFT driver, and the framebuffer will be left
|
||
unconfigured.
|
||
b - Enable backlight. The TFT backlight pin will be
|
||
linked to the kernel VESA blanking code and a GPIO
|
||
LED. This parameter is not necessary when using the
|
||
VGA shield.
|
||
c - Enable the s3c camera interface.
|
||
t - Reserved for enabling touchscreen support. The
|
||
touchscreen support is not enabled in the mainstream
|
||
kernel as of 2.6.30, a preliminary port can be found
|
||
in the "bleeding edge" mini2440 support kernel at
|
||
https://repo.or.cz/w/linux-2.6/mini2440.git
|
||
|
||
mitigations=
|
||
[X86,PPC,S390,ARM64,EARLY] Control optional mitigations for
|
||
CPU vulnerabilities. This is a set of curated,
|
||
arch-independent options, each of which is an
|
||
aggregation of existing arch-specific options.
|
||
|
||
Note, "mitigations" is supported if and only if the
|
||
kernel was built with CPU_MITIGATIONS=y.
|
||
|
||
off
|
||
Disable all optional CPU mitigations. This
|
||
improves system performance, but it may also
|
||
expose users to several CPU vulnerabilities.
|
||
Equivalent to: if nokaslr then kpti=0 [ARM64]
|
||
gather_data_sampling=off [X86]
|
||
kvm.nx_huge_pages=off [X86]
|
||
l1tf=off [X86]
|
||
mds=off [X86]
|
||
mmio_stale_data=off [X86]
|
||
no_entry_flush [PPC]
|
||
no_uaccess_flush [PPC]
|
||
nobp=0 [S390]
|
||
nopti [X86,PPC]
|
||
nospectre_bhb [ARM64]
|
||
nospectre_v1 [X86,PPC]
|
||
nospectre_v2 [X86,PPC,S390,ARM64]
|
||
reg_file_data_sampling=off [X86]
|
||
retbleed=off [X86]
|
||
spec_rstack_overflow=off [X86]
|
||
spec_store_bypass_disable=off [X86,PPC]
|
||
spectre_bhi=off [X86]
|
||
spectre_v2_user=off [X86]
|
||
srbds=off [X86,INTEL]
|
||
ssbd=force-off [ARM64]
|
||
tsx_async_abort=off [X86]
|
||
|
||
Exceptions:
|
||
This does not have any effect on
|
||
kvm.nx_huge_pages when
|
||
kvm.nx_huge_pages=force.
|
||
|
||
auto (default)
|
||
Mitigate all CPU vulnerabilities, but leave SMT
|
||
enabled, even if it's vulnerable. This is for
|
||
users who don't want to be surprised by SMT
|
||
getting disabled across kernel upgrades, or who
|
||
have other ways of avoiding SMT-based attacks.
|
||
Equivalent to: (default behavior)
|
||
|
||
auto,nosmt
|
||
Mitigate all CPU vulnerabilities, disabling SMT
|
||
if needed. This is for users who always want to
|
||
be fully mitigated, even if it means losing SMT.
|
||
Equivalent to: l1tf=flush,nosmt [X86]
|
||
mds=full,nosmt [X86]
|
||
tsx_async_abort=full,nosmt [X86]
|
||
mmio_stale_data=full,nosmt [X86]
|
||
retbleed=auto,nosmt [X86]
|
||
|
||
mminit_loglevel=
|
||
[KNL,EARLY] When CONFIG_DEBUG_MEMORY_INIT is set, this
|
||
parameter allows control of the logging verbosity for
|
||
the additional memory initialisation checks. A value
|
||
of 0 disables mminit logging and a level of 4 will
|
||
log everything. Information is printed at KERN_DEBUG
|
||
so loglevel=8 may also need to be specified.
|
||
|
||
mmio_stale_data=
|
||
[X86,INTEL,EARLY] Control mitigation for the Processor
|
||
MMIO Stale Data vulnerabilities.
|
||
|
||
Processor MMIO Stale Data is a class of
|
||
vulnerabilities that may expose data after an MMIO
|
||
operation. Exposed data could originate or end in
|
||
the same CPU buffers as affected by MDS and TAA.
|
||
Therefore, similar to MDS and TAA, the mitigation
|
||
is to clear the affected CPU buffers.
|
||
|
||
This parameter controls the mitigation. The
|
||
options are:
|
||
|
||
full - Enable mitigation on vulnerable CPUs
|
||
|
||
full,nosmt - Enable mitigation and disable SMT on
|
||
vulnerable CPUs.
|
||
|
||
off - Unconditionally disable mitigation
|
||
|
||
On MDS or TAA affected machines,
|
||
mmio_stale_data=off can be prevented by an active
|
||
MDS or TAA mitigation as these vulnerabilities are
|
||
mitigated with the same mechanism so in order to
|
||
disable this mitigation, you need to specify
|
||
mds=off and tsx_async_abort=off too.
|
||
|
||
Not specifying this option is equivalent to
|
||
mmio_stale_data=full.
|
||
|
||
For details see:
|
||
Documentation/admin-guide/hw-vuln/processor_mmio_stale_data.rst
|
||
|
||
<module>.async_probe[=<bool>] [KNL]
|
||
If no <bool> value is specified or if the value
|
||
specified is not a valid <bool>, enable asynchronous
|
||
probe on this module. Otherwise, enable/disable
|
||
asynchronous probe on this module as indicated by the
|
||
<bool> value. See also: module.async_probe
|
||
|
||
module.async_probe=<bool>
|
||
[KNL] When set to true, modules will use async probing
|
||
by default. To enable/disable async probing for a
|
||
specific module, use the module specific control that
|
||
is documented under <module>.async_probe. When both
|
||
module.async_probe and <module>.async_probe are
|
||
specified, <module>.async_probe takes precedence for
|
||
the specific module.
|
||
|
||
module.enable_dups_trace
|
||
[KNL] When CONFIG_MODULE_DEBUG_AUTOLOAD_DUPS is set,
|
||
this means that duplicate request_module() calls will
|
||
trigger a WARN_ON() instead of a pr_warn(). Note that
|
||
if MODULE_DEBUG_AUTOLOAD_DUPS_TRACE is set, WARN_ON()s
|
||
will always be issued and this option does nothing.
|
||
module.sig_enforce
|
||
[KNL] When CONFIG_MODULE_SIG is set, this means that
|
||
modules without (valid) signatures will fail to load.
|
||
Note that if CONFIG_MODULE_SIG_FORCE is set, that
|
||
is always true, so this option does nothing.
|
||
|
||
module_blacklist= [KNL] Do not load a comma-separated list of
|
||
modules. Useful for debugging problem modules.
|
||
|
||
mousedev.tap_time=
|
||
[MOUSE] Maximum time between finger touching and
|
||
leaving touchpad surface for touch to be considered
|
||
a tap and be reported as a left button click (for
|
||
touchpads working in absolute mode only).
|
||
Format: <msecs>
|
||
mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
|
||
reporting absolute coordinates, such as tablets
|
||
mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
|
||
reporting absolute coordinates, such as tablets
|
||
|
||
movablecore= [KNL,X86,PPC,EARLY]
|
||
Format: nn[KMGTPE] | nn%
|
||
This parameter is the complement to kernelcore=, it
|
||
specifies the amount of memory used for migratable
|
||
allocations. If both kernelcore and movablecore is
|
||
specified, then kernelcore will be at *least* the
|
||
specified value but may be more. If movablecore on its
|
||
own is specified, the administrator must be careful
|
||
that the amount of memory usable for all allocations
|
||
is not too small.
|
||
|
||
movable_node [KNL,EARLY] Boot-time switch to make hotplugable memory
|
||
NUMA nodes to be movable. This means that the memory
|
||
of such nodes will be usable only for movable
|
||
allocations which rules out almost all kernel
|
||
allocations. Use with caution!
|
||
|
||
MTD_Partition= [MTD]
|
||
Format: <name>,<region-number>,<size>,<offset>
|
||
|
||
MTD_Region= [MTD] Format:
|
||
<name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
|
||
|
||
mtdparts= [MTD]
|
||
See drivers/mtd/parsers/cmdlinepart.c
|
||
|
||
mtouchusb.raw_coordinates=
|
||
[HW] Make the MicroTouch USB driver use raw coordinates
|
||
('y', default) or cooked coordinates ('n')
|
||
|
||
mtrr=debug [X86,EARLY]
|
||
Enable printing debug information related to MTRR
|
||
registers at boot time.
|
||
|
||
mtrr_chunk_size=nn[KMG,X86,EARLY]
|
||
used for mtrr cleanup. It is largest continuous chunk
|
||
that could hold holes aka. UC entries.
|
||
|
||
mtrr_gran_size=nn[KMG,X86,EARLY]
|
||
Used for mtrr cleanup. It is granularity of mtrr block.
|
||
Default is 1.
|
||
Large value could prevent small alignment from
|
||
using up MTRRs.
|
||
|
||
mtrr_spare_reg_nr=n [X86,EARLY]
|
||
Format: <integer>
|
||
Range: 0,7 : spare reg number
|
||
Default : 1
|
||
Used for mtrr cleanup. It is spare mtrr entries number.
|
||
Set to 2 or more if your graphical card needs more.
|
||
|
||
multitce=off [PPC] This parameter disables the use of the pSeries
|
||
firmware feature for updating multiple TCE entries
|
||
at a time.
|
||
|
||
n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
|
||
|
||
netdev= [NET] Network devices parameters
|
||
Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
|
||
Note that mem_start is often overloaded to mean
|
||
something different and driver-specific.
|
||
This usage is only documented in each driver source
|
||
file if at all.
|
||
|
||
netpoll.carrier_timeout=
|
||
[NET] Specifies amount of time (in seconds) that
|
||
netpoll should wait for a carrier. By default netpoll
|
||
waits 4 seconds.
|
||
|
||
nf_conntrack.acct=
|
||
[NETFILTER] Enable connection tracking flow accounting
|
||
0 to disable accounting
|
||
1 to enable accounting
|
||
Default value is 0.
|
||
|
||
nfs.cache_getent=
|
||
[NFS] sets the pathname to the program which is used
|
||
to update the NFS client cache entries.
|
||
|
||
nfs.cache_getent_timeout=
|
||
[NFS] sets the timeout after which an attempt to
|
||
update a cache entry is deemed to have failed.
|
||
|
||
nfs.callback_nr_threads=
|
||
[NFSv4] set the total number of threads that the
|
||
NFS client will assign to service NFSv4 callback
|
||
requests.
|
||
|
||
nfs.callback_tcpport=
|
||
[NFS] set the TCP port on which the NFSv4 callback
|
||
channel should listen.
|
||
|
||
nfs.delay_retrans=
|
||
[NFS] specifies the number of times the NFSv4 client
|
||
retries the request before returning an EAGAIN error,
|
||
after a reply of NFS4ERR_DELAY from the server.
|
||
Only applies if the softerr mount option is enabled,
|
||
and the specified value is >= 0.
|
||
|
||
nfs.enable_ino64=
|
||
[NFS] enable 64-bit inode numbers.
|
||
If zero, the NFS client will fake up a 32-bit inode
|
||
number for the readdir() and stat() syscalls instead
|
||
of returning the full 64-bit number.
|
||
The default is to return 64-bit inode numbers.
|
||
|
||
nfs.idmap_cache_timeout=
|
||
[NFS] set the maximum lifetime for idmapper cache
|
||
entries.
|
||
|
||
nfs.max_session_cb_slots=
|
||
[NFSv4.1] Sets the maximum number of session
|
||
slots the client will assign to the callback
|
||
channel. This determines the maximum number of
|
||
callbacks the client will process in parallel for
|
||
a particular server.
|
||
|
||
nfs.max_session_slots=
|
||
[NFSv4.1] Sets the maximum number of session slots
|
||
the client will attempt to negotiate with the server.
|
||
This limits the number of simultaneous RPC requests
|
||
that the client can send to the NFSv4.1 server.
|
||
Note that there is little point in setting this
|
||
value higher than the max_tcp_slot_table_limit.
|
||
|
||
nfs.nfs4_disable_idmapping=
|
||
[NFSv4] When set to the default of '1', this option
|
||
ensures that both the RPC level authentication
|
||
scheme and the NFS level operations agree to use
|
||
numeric uids/gids if the mount is using the
|
||
'sec=sys' security flavour. In effect it is
|
||
disabling idmapping, which can make migration from
|
||
legacy NFSv2/v3 systems to NFSv4 easier.
|
||
Servers that do not support this mode of operation
|
||
will be autodetected by the client, and it will fall
|
||
back to using the idmapper.
|
||
To turn off this behaviour, set the value to '0'.
|
||
|
||
nfs.nfs4_unique_id=
|
||
[NFS4] Specify an additional fixed unique ident-
|
||
ification string that NFSv4 clients can insert into
|
||
their nfs_client_id4 string. This is typically a
|
||
UUID that is generated at system install time.
|
||
|
||
nfs.recover_lost_locks=
|
||
[NFSv4] Attempt to recover locks that were lost due
|
||
to a lease timeout on the server. Please note that
|
||
doing this risks data corruption, since there are
|
||
no guarantees that the file will remain unchanged
|
||
after the locks are lost.
|
||
If you want to enable the kernel legacy behaviour of
|
||
attempting to recover these locks, then set this
|
||
parameter to '1'.
|
||
The default parameter value of '0' causes the kernel
|
||
not to attempt recovery of lost locks.
|
||
|
||
nfs.send_implementation_id=
|
||
[NFSv4.1] Send client implementation identification
|
||
information in exchange_id requests.
|
||
If zero, no implementation identification information
|
||
will be sent.
|
||
The default is to send the implementation identification
|
||
information.
|
||
|
||
nfs4.layoutstats_timer=
|
||
[NFSv4.2] Change the rate at which the kernel sends
|
||
layoutstats to the pNFS metadata server.
|
||
|
||
Setting this to value to 0 causes the kernel to use
|
||
whatever value is the default set by the layout
|
||
driver. A non-zero value sets the minimum interval
|
||
in seconds between layoutstats transmissions.
|
||
|
||
nfsd.inter_copy_offload_enable=
|
||
[NFSv4.2] When set to 1, the server will support
|
||
server-to-server copies for which this server is
|
||
the destination of the copy.
|
||
|
||
nfsd.nfs4_disable_idmapping=
|
||
[NFSv4] When set to the default of '1', the NFSv4
|
||
server will return only numeric uids and gids to
|
||
clients using auth_sys, and will accept numeric uids
|
||
and gids from such clients. This is intended to ease
|
||
migration from NFSv2/v3.
|
||
|
||
nfsd.nfsd4_ssc_umount_timeout=
|
||
[NFSv4.2] When used as the destination of a
|
||
server-to-server copy, knfsd temporarily mounts
|
||
the source server. It caches the mount in case
|
||
it will be needed again, and discards it if not
|
||
used for the number of milliseconds specified by
|
||
this parameter.
|
||
|
||
nfsaddrs= [NFS] Deprecated. Use ip= instead.
|
||
See Documentation/admin-guide/nfs/nfsroot.rst.
|
||
|
||
nfsroot= [NFS] nfs root filesystem for disk-less boxes.
|
||
See Documentation/admin-guide/nfs/nfsroot.rst.
|
||
|
||
nfsrootdebug [NFS] enable nfsroot debugging messages.
|
||
See Documentation/admin-guide/nfs/nfsroot.rst.
|
||
|
||
nmi_backtrace.backtrace_idle [KNL]
|
||
Dump stacks even of idle CPUs in response to an
|
||
NMI stack-backtrace request.
|
||
|
||
nmi_debug= [KNL,SH] Specify one or more actions to take
|
||
when a NMI is triggered.
|
||
Format: [state][,regs][,debounce][,die]
|
||
|
||
nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
|
||
Format: [panic,][nopanic,][rNNN,][num]
|
||
Valid num: 0 or 1
|
||
0 - turn hardlockup detector in nmi_watchdog off
|
||
1 - turn hardlockup detector in nmi_watchdog on
|
||
rNNN - configure the watchdog with raw perf event 0xNNN
|
||
|
||
When panic is specified, panic when an NMI watchdog
|
||
timeout occurs (or 'nopanic' to not panic on an NMI
|
||
watchdog, if CONFIG_BOOTPARAM_HARDLOCKUP_PANIC is set)
|
||
To disable both hard and soft lockup detectors,
|
||
please see 'nowatchdog'.
|
||
This is useful when you use a panic=... timeout and
|
||
need the box quickly up again.
|
||
|
||
These settings can be accessed at runtime via
|
||
the nmi_watchdog and hardlockup_panic sysctls.
|
||
|
||
no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
|
||
emulation library even if a 387 maths coprocessor
|
||
is present.
|
||
|
||
no4lvl [RISCV,EARLY] Disable 4-level and 5-level paging modes.
|
||
Forces kernel to use 3-level paging instead.
|
||
|
||
no5lvl [X86-64,RISCV,EARLY] Disable 5-level paging mode. Forces
|
||
kernel to use 4-level paging instead.
|
||
|
||
noalign [KNL,ARM]
|
||
|
||
noapic [SMP,APIC,EARLY] Tells the kernel to not make use of any
|
||
IOAPICs that may be present in the system.
|
||
|
||
noautogroup Disable scheduler automatic task group creation.
|
||
|
||
nocache [ARM,EARLY]
|
||
|
||
no_console_suspend
|
||
[HW] Never suspend the console
|
||
Disable suspending of consoles during suspend and
|
||
hibernate operations. Once disabled, debugging
|
||
messages can reach various consoles while the rest
|
||
of the system is being put to sleep (ie, while
|
||
debugging driver suspend/resume hooks). This may
|
||
not work reliably with all consoles, but is known
|
||
to work with serial and VGA consoles.
|
||
To facilitate more flexible debugging, we also add
|
||
console_suspend, a printk module parameter to control
|
||
it. Users could use console_suspend (usually
|
||
/sys/module/printk/parameters/console_suspend) to
|
||
turn on/off it dynamically.
|
||
|
||
no_debug_objects
|
||
[KNL,EARLY] Disable object debugging
|
||
|
||
nodsp [SH] Disable hardware DSP at boot time.
|
||
|
||
noefi [EFI,EARLY] Disable EFI runtime services support.
|
||
|
||
no_entry_flush [PPC,EARLY] Don't flush the L1-D cache when entering the kernel.
|
||
|
||
noexec32 [X86-64]
|
||
This affects only 32-bit executables.
|
||
noexec32=on: enable non-executable mappings (default)
|
||
read doesn't imply executable mappings
|
||
noexec32=off: disable non-executable mappings
|
||
read implies executable mappings
|
||
|
||
no_file_caps Tells the kernel not to honor file capabilities. The
|
||
only way then for a file to be executed with privilege
|
||
is to be setuid root or executed by root.
|
||
|
||
nofpu [MIPS,SH] Disable hardware FPU at boot time.
|
||
|
||
nofsgsbase [X86] Disables FSGSBASE instructions.
|
||
|
||
nofxsr [BUGS=X86-32] Disables x86 floating point extended
|
||
register save and restore. The kernel will only save
|
||
legacy floating-point registers on task switch.
|
||
|
||
no_hash_pointers
|
||
[KNL,EARLY]
|
||
Force pointers printed to the console or buffers to be
|
||
unhashed. By default, when a pointer is printed via %p
|
||
format string, that pointer is "hashed", i.e. obscured
|
||
by hashing the pointer value. This is a security feature
|
||
that hides actual kernel addresses from unprivileged
|
||
users, but it also makes debugging the kernel more
|
||
difficult since unequal pointers can no longer be
|
||
compared. However, if this command-line option is
|
||
specified, then all normal pointers will have their true
|
||
value printed. This option should only be specified when
|
||
debugging the kernel. Please do not use on production
|
||
kernels.
|
||
|
||
nohibernate [HIBERNATION] Disable hibernation and resume.
|
||
|
||
nohlt [ARM,ARM64,MICROBLAZE,MIPS,PPC,RISCV,SH] Forces the kernel to
|
||
busy wait in do_idle() and not use the arch_cpu_idle()
|
||
implementation; requires CONFIG_GENERIC_IDLE_POLL_SETUP
|
||
to be effective. This is useful on platforms where the
|
||
sleep(SH) or wfi(ARM,ARM64) instructions do not work
|
||
correctly or when doing power measurements to evaluate
|
||
the impact of the sleep instructions. This is also
|
||
useful when using JTAG debugger.
|
||
|
||
nohugeiomap [KNL,X86,PPC,ARM64,EARLY] Disable kernel huge I/O mappings.
|
||
|
||
nohugevmalloc [KNL,X86,PPC,ARM64,EARLY] Disable kernel huge vmalloc mappings.
|
||
|
||
nohz= [KNL] Boottime enable/disable dynamic ticks
|
||
Valid arguments: on, off
|
||
Default: on
|
||
|
||
nohz_full= [KNL,BOOT,SMP,ISOL]
|
||
The argument is a cpu list, as described above.
|
||
In kernels built with CONFIG_NO_HZ_FULL=y, set
|
||
the specified list of CPUs whose tick will be stopped
|
||
whenever possible. The boot CPU will be forced outside
|
||
the range to maintain the timekeeping. Any CPUs
|
||
in this list will have their RCU callbacks offloaded,
|
||
just as if they had also been called out in the
|
||
rcu_nocbs= boot parameter.
|
||
|
||
Note that this argument takes precedence over
|
||
the CONFIG_RCU_NOCB_CPU_DEFAULT_ALL option.
|
||
|
||
noinitrd [RAM] Tells the kernel not to load any configured
|
||
initial RAM disk.
|
||
|
||
nointremap [X86-64,Intel-IOMMU,EARLY] Do not enable interrupt
|
||
remapping.
|
||
[Deprecated - use intremap=off]
|
||
|
||
noinvpcid [X86,EARLY] Disable the INVPCID cpu feature.
|
||
|
||
noiotrap [SH] Disables trapped I/O port accesses.
|
||
|
||
noirqdebug [X86-32] Disables the code which attempts to detect and
|
||
disable unhandled interrupt sources.
|
||
|
||
noisapnp [ISAPNP] Disables ISA PnP code.
|
||
|
||
nokaslr [KNL,EARLY]
|
||
When CONFIG_RANDOMIZE_BASE is set, this disables
|
||
kernel and module base offset ASLR (Address Space
|
||
Layout Randomization).
|
||
|
||
no-kvmapf [X86,KVM,EARLY] Disable paravirtualized asynchronous page
|
||
fault handling.
|
||
|
||
no-kvmclock [X86,KVM,EARLY] Disable paravirtualized KVM clock driver
|
||
|
||
nolapic [X86-32,APIC,EARLY] Do not enable or use the local APIC.
|
||
|
||
nolapic_timer [X86-32,APIC,EARLY] Do not use the local APIC timer.
|
||
|
||
nomce [X86-32] Disable Machine Check Exception
|
||
|
||
nomfgpt [X86-32] Disable Multi-Function General Purpose
|
||
Timer usage (for AMD Geode machines).
|
||
|
||
nomodeset Disable kernel modesetting. Most systems' firmware
|
||
sets up a display mode and provides framebuffer memory
|
||
for output. With nomodeset, DRM and fbdev drivers will
|
||
not load if they could possibly displace the pre-
|
||
initialized output. Only the system framebuffer will
|
||
be available for use. The respective drivers will not
|
||
perform display-mode changes or accelerated rendering.
|
||
|
||
Useful as error fallback, or for testing and debugging.
|
||
|
||
nomodule Disable module load
|
||
|
||
nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
|
||
shutdown the other cpus. Instead use the REBOOT_VECTOR
|
||
irq.
|
||
|
||
nopat [X86,EARLY] Disable PAT (page attribute table extension of
|
||
pagetables) support.
|
||
|
||
nopcid [X86-64,EARLY] Disable the PCID cpu feature.
|
||
|
||
nopku [X86] Disable Memory Protection Keys CPU feature found
|
||
in some Intel CPUs.
|
||
|
||
nopti [X86-64,EARLY]
|
||
Equivalent to pti=off
|
||
|
||
nopv= [X86,XEN,KVM,HYPER_V,VMWARE,EARLY]
|
||
Disables the PV optimizations forcing the guest to run
|
||
as generic guest with no PV drivers. Currently support
|
||
XEN HVM, KVM, HYPER_V and VMWARE guest.
|
||
|
||
nopvspin [X86,XEN,KVM,EARLY]
|
||
Disables the qspinlock slow path using PV optimizations
|
||
which allow the hypervisor to 'idle' the guest on lock
|
||
contention.
|
||
|
||
norandmaps Don't use address space randomization. Equivalent to
|
||
echo 0 > /proc/sys/kernel/randomize_va_space
|
||
|
||
noreplace-smp [X86-32,SMP] Don't replace SMP instructions
|
||
with UP alternatives
|
||
|
||
noresume [SWSUSP] Disables resume and restores original swap
|
||
space.
|
||
|
||
no-scroll [VGA] Disables scrollback.
|
||
This is required for the Braillex ib80-piezo Braille
|
||
reader made by F.H. Papenmeier (Germany).
|
||
|
||
nosgx [X86-64,SGX,EARLY] Disables Intel SGX kernel support.
|
||
|
||
nosmap [PPC,EARLY]
|
||
Disable SMAP (Supervisor Mode Access Prevention)
|
||
even if it is supported by processor.
|
||
|
||
nosmep [PPC64s,EARLY]
|
||
Disable SMEP (Supervisor Mode Execution Prevention)
|
||
even if it is supported by processor.
|
||
|
||
nosmp [SMP,EARLY] Tells an SMP kernel to act as a UP kernel,
|
||
and disable the IO APIC. legacy for "maxcpus=0".
|
||
|
||
nosmt [KNL,MIPS,PPC,S390,EARLY] Disable symmetric multithreading (SMT).
|
||
Equivalent to smt=1.
|
||
|
||
[KNL,X86,PPC] Disable symmetric multithreading (SMT).
|
||
nosmt=force: Force disable SMT, cannot be undone
|
||
via the sysfs control file.
|
||
|
||
nosoftlockup [KNL] Disable the soft-lockup detector.
|
||
|
||
nospec_store_bypass_disable
|
||
[HW,EARLY] Disable all mitigations for the Speculative
|
||
Store Bypass vulnerability
|
||
|
||
nospectre_bhb [ARM64,EARLY] Disable all mitigations for Spectre-BHB (branch
|
||
history injection) vulnerability. System may allow data leaks
|
||
with this option.
|
||
|
||
nospectre_v1 [X86,PPC,EARLY] Disable mitigations for Spectre Variant 1
|
||
(bounds check bypass). With this option data leaks are
|
||
possible in the system.
|
||
|
||
nospectre_v2 [X86,PPC_E500,ARM64,EARLY] Disable all mitigations
|
||
for the Spectre variant 2 (indirect branch
|
||
prediction) vulnerability. System may allow data
|
||
leaks with this option.
|
||
|
||
no-steal-acc [X86,PV_OPS,ARM64,PPC/PSERIES,RISCV,LOONGARCH,EARLY]
|
||
Disable paravirtualized steal time accounting. steal time
|
||
is computed, but won't influence scheduler behaviour
|
||
|
||
nosync [HW,M68K] Disables sync negotiation for all devices.
|
||
|
||
no_timer_check [X86,APIC] Disables the code which tests for
|
||
broken timer IRQ sources.
|
||
|
||
no_uaccess_flush
|
||
[PPC,EARLY] Don't flush the L1-D cache after accessing user data.
|
||
|
||
novmcoredd [KNL,KDUMP]
|
||
Disable device dump. Device dump allows drivers to
|
||
append dump data to vmcore so you can collect driver
|
||
specified debug info. Drivers can append the data
|
||
without any limit and this data is stored in memory,
|
||
so this may cause significant memory stress. Disabling
|
||
device dump can help save memory but the driver debug
|
||
data will be no longer available. This parameter
|
||
is only available when CONFIG_PROC_VMCORE_DEVICE_DUMP
|
||
is set.
|
||
|
||
no-vmw-sched-clock
|
||
[X86,PV_OPS,EARLY] Disable paravirtualized VMware
|
||
scheduler clock and use the default one.
|
||
|
||
nowatchdog [KNL] Disable both lockup detectors, i.e.
|
||
soft-lockup and NMI watchdog (hard-lockup).
|
||
|
||
nowb [ARM,EARLY]
|
||
|
||
nox2apic [X86-64,APIC,EARLY] Do not enable x2APIC mode.
|
||
|
||
NOTE: this parameter will be ignored on systems with the
|
||
LEGACY_XAPIC_DISABLED bit set in the
|
||
IA32_XAPIC_DISABLE_STATUS MSR.
|
||
|
||
noxsave [BUGS=X86] Disables x86 extended register state save
|
||
and restore using xsave. The kernel will fallback to
|
||
enabling legacy floating-point and sse state.
|
||
|
||
noxsaveopt [X86] Disables xsaveopt used in saving x86 extended
|
||
register states. The kernel will fall back to use
|
||
xsave to save the states. By using this parameter,
|
||
performance of saving the states is degraded because
|
||
xsave doesn't support modified optimization while
|
||
xsaveopt supports it on xsaveopt enabled systems.
|
||
|
||
noxsaves [X86] Disables xsaves and xrstors used in saving and
|
||
restoring x86 extended register state in compacted
|
||
form of xsave area. The kernel will fall back to use
|
||
xsaveopt and xrstor to save and restore the states
|
||
in standard form of xsave area. By using this
|
||
parameter, xsave area per process might occupy more
|
||
memory on xsaves enabled systems.
|
||
|
||
nr_cpus= [SMP,EARLY] Maximum number of processors that an SMP kernel
|
||
could support. nr_cpus=n : n >= 1 limits the kernel to
|
||
support 'n' processors. It could be larger than the
|
||
number of already plugged CPU during bootup, later in
|
||
runtime you can physically add extra cpu until it reaches
|
||
n. So during boot up some boot time memory for per-cpu
|
||
variables need be pre-allocated for later physical cpu
|
||
hot plugging.
|
||
|
||
nr_uarts= [SERIAL] maximum number of UARTs to be registered.
|
||
|
||
numa=off [KNL, ARM64, PPC, RISCV, SPARC, X86, EARLY]
|
||
Disable NUMA, Only set up a single NUMA node
|
||
spanning all memory.
|
||
|
||
numa=fake=<size>[MG]
|
||
[KNL, ARM64, RISCV, X86, EARLY]
|
||
If given as a memory unit, fills all system RAM with
|
||
nodes of size interleaved over physical nodes.
|
||
|
||
numa=fake=<N>
|
||
[KNL, ARM64, RISCV, X86, EARLY]
|
||
If given as an integer, fills all system RAM with N
|
||
fake nodes interleaved over physical nodes.
|
||
|
||
numa=fake=<N>U
|
||
[KNL, ARM64, RISCV, X86, EARLY]
|
||
If given as an integer followed by 'U', it will
|
||
divide each physical node into N emulated nodes.
|
||
|
||
numa_balancing= [KNL,ARM64,PPC,RISCV,S390,X86] Enable or disable automatic
|
||
NUMA balancing.
|
||
Allowed values are enable and disable
|
||
|
||
numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
|
||
'node', 'default' can be specified
|
||
This can be set from sysctl after boot.
|
||
See Documentation/admin-guide/sysctl/vm.rst for details.
|
||
|
||
ohci1394_dma=early [HW,EARLY] enable debugging via the ohci1394 driver.
|
||
See Documentation/core-api/debugging-via-ohci1394.rst for more
|
||
info.
|
||
|
||
olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
|
||
Rather than timing out after 20 ms if an EC
|
||
command is not properly ACKed, override the length
|
||
of the timeout. We have interrupts disabled while
|
||
waiting for the ACK, so if this is set too high
|
||
interrupts *may* be lost!
|
||
|
||
omap_mux= [OMAP] Override bootloader pin multiplexing.
|
||
Format: <mux_mode0.mode_name=value>...
|
||
For example, to override I2C bus2:
|
||
omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
|
||
|
||
onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
|
||
|
||
Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
|
||
|
||
boundary - index of last SLC block on Flex-OneNAND.
|
||
The remaining blocks are configured as MLC blocks.
|
||
lock - Configure if Flex-OneNAND boundary should be locked.
|
||
Once locked, the boundary cannot be changed.
|
||
1 indicates lock status, 0 indicates unlock status.
|
||
|
||
oops=panic [KNL,EARLY]
|
||
Always panic on oopses. Default is to just kill the
|
||
process, but there is a small probability of
|
||
deadlocking the machine.
|
||
This will also cause panics on machine check exceptions.
|
||
Useful together with panic=30 to trigger a reboot.
|
||
|
||
page_alloc.shuffle=
|
||
[KNL] Boolean flag to control whether the page allocator
|
||
should randomize its free lists. This parameter can be
|
||
used to enable/disable page randomization. The state of
|
||
the flag can be read from sysfs at:
|
||
/sys/module/page_alloc/parameters/shuffle.
|
||
This parameter is only available if CONFIG_SHUFFLE_PAGE_ALLOCATOR=y.
|
||
|
||
page_owner= [KNL,EARLY] Boot-time page_owner enabling option.
|
||
Storage of the information about who allocated
|
||
each page is disabled in default. With this switch,
|
||
we can turn it on.
|
||
on: enable the feature
|
||
|
||
page_poison= [KNL,EARLY] Boot-time parameter changing the state of
|
||
poisoning on the buddy allocator, available with
|
||
CONFIG_PAGE_POISONING=y.
|
||
off: turn off poisoning (default)
|
||
on: turn on poisoning
|
||
|
||
page_reporting.page_reporting_order=
|
||
[KNL] Minimal page reporting order
|
||
Format: <integer>
|
||
Adjust the minimal page reporting order. The page
|
||
reporting is disabled when it exceeds MAX_PAGE_ORDER.
|
||
|
||
panic= [KNL] Kernel behaviour on panic: delay <timeout>
|
||
timeout > 0: seconds before rebooting
|
||
timeout = 0: wait forever
|
||
timeout < 0: reboot immediately
|
||
Format: <timeout>
|
||
|
||
panic_on_taint= [KNL,EARLY]
|
||
Bitmask for conditionally calling panic() in add_taint()
|
||
Format: <hex>[,nousertaint]
|
||
Hexadecimal bitmask representing the set of TAINT flags
|
||
that will cause the kernel to panic when add_taint() is
|
||
called with any of the flags in this set.
|
||
The optional switch "nousertaint" can be utilized to
|
||
prevent userspace forced crashes by writing to sysctl
|
||
/proc/sys/kernel/tainted any flagset matching with the
|
||
bitmask set on panic_on_taint.
|
||
See Documentation/admin-guide/tainted-kernels.rst for
|
||
extra details on the taint flags that users can pick
|
||
to compose the bitmask to assign to panic_on_taint.
|
||
|
||
panic_on_warn=1 panic() instead of WARN(). Useful to cause kdump
|
||
on a WARN().
|
||
|
||
panic_print= Bitmask for printing system info when panic happens.
|
||
User can chose combination of the following bits:
|
||
bit 0: print all tasks info
|
||
bit 1: print system memory info
|
||
bit 2: print timer info
|
||
bit 3: print locks info if CONFIG_LOCKDEP is on
|
||
bit 4: print ftrace buffer
|
||
bit 5: print all printk messages in buffer
|
||
bit 6: print all CPUs backtrace (if available in the arch)
|
||
bit 7: print only tasks in uninterruptible (blocked) state
|
||
*Be aware* that this option may print a _lot_ of lines,
|
||
so there are risks of losing older messages in the log.
|
||
Use this option carefully, maybe worth to setup a
|
||
bigger log buffer with "log_buf_len" along with this.
|
||
|
||
parkbd.port= [HW] Parallel port number the keyboard adapter is
|
||
connected to, default is 0.
|
||
Format: <parport#>
|
||
parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
|
||
0 for XT, 1 for AT (default is AT).
|
||
Format: <mode>
|
||
|
||
parport= [HW,PPT] Specify parallel ports. 0 disables.
|
||
Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
|
||
Use 'auto' to force the driver to use any
|
||
IRQ/DMA settings detected (the default is to
|
||
ignore detected IRQ/DMA settings because of
|
||
possible conflicts). You can specify the base
|
||
address, IRQ, and DMA settings; IRQ and DMA
|
||
should be numbers, or 'auto' (for using detected
|
||
settings on that particular port), or 'nofifo'
|
||
(to avoid using a FIFO even if it is detected).
|
||
Parallel ports are assigned in the order they
|
||
are specified on the command line, starting
|
||
with parport0.
|
||
|
||
parport_init_mode= [HW,PPT]
|
||
Configure VIA parallel port to operate in
|
||
a specific mode. This is necessary on Pegasos
|
||
computer where firmware has no options for setting
|
||
up parallel port mode and sets it to spp.
|
||
Currently this function knows 686a and 8231 chips.
|
||
Format: [spp|ps2|epp|ecp|ecpepp]
|
||
|
||
pata_legacy.all= [HW,LIBATA]
|
||
Format: <int>
|
||
Set to non-zero to probe primary and secondary ISA
|
||
port ranges on PCI systems where no PCI PATA device
|
||
has been found at either range. Disabled by default.
|
||
|
||
pata_legacy.autospeed= [HW,LIBATA]
|
||
Format: <int>
|
||
Set to non-zero if a chip is present that snoops speed
|
||
changes. Disabled by default.
|
||
|
||
pata_legacy.ht6560a= [HW,LIBATA]
|
||
Format: <int>
|
||
Set to 1, 2, or 3 for HT 6560A on the primary channel,
|
||
the secondary channel, or both channels respectively.
|
||
Disabled by default.
|
||
|
||
pata_legacy.ht6560b= [HW,LIBATA]
|
||
Format: <int>
|
||
Set to 1, 2, or 3 for HT 6560B on the primary channel,
|
||
the secondary channel, or both channels respectively.
|
||
Disabled by default.
|
||
|
||
pata_legacy.iordy_mask= [HW,LIBATA]
|
||
Format: <int>
|
||
IORDY enable mask. Set individual bits to allow IORDY
|
||
for the respective channel. Bit 0 is for the first
|
||
legacy channel handled by this driver, bit 1 is for
|
||
the second channel, and so on. The sequence will often
|
||
correspond to the primary legacy channel, the secondary
|
||
legacy channel, and so on, but the handling of a PCI
|
||
bus and the use of other driver options may interfere
|
||
with the sequence. By default IORDY is allowed across
|
||
all channels.
|
||
|
||
pata_legacy.opti82c46x= [HW,LIBATA]
|
||
Format: <int>
|
||
Set to 1, 2, or 3 for Opti 82c611A on the primary
|
||
channel, the secondary channel, or both channels
|
||
respectively. Disabled by default.
|
||
|
||
pata_legacy.opti82c611a= [HW,LIBATA]
|
||
Format: <int>
|
||
Set to 1, 2, or 3 for Opti 82c465MV on the primary
|
||
channel, the secondary channel, or both channels
|
||
respectively. Disabled by default.
|
||
|
||
pata_legacy.pio_mask= [HW,LIBATA]
|
||
Format: <int>
|
||
PIO mode mask for autospeed devices. Set individual
|
||
bits to allow the use of the respective PIO modes.
|
||
Bit 0 is for mode 0, bit 1 is for mode 1, and so on.
|
||
All modes allowed by default.
|
||
|
||
pata_legacy.probe_all= [HW,LIBATA]
|
||
Format: <int>
|
||
Set to non-zero to probe tertiary and further ISA
|
||
port ranges on PCI systems. Disabled by default.
|
||
|
||
pata_legacy.probe_mask= [HW,LIBATA]
|
||
Format: <int>
|
||
Probe mask for legacy ISA PATA ports. Depending on
|
||
platform configuration and the use of other driver
|
||
options up to 6 legacy ports are supported: 0x1f0,
|
||
0x170, 0x1e8, 0x168, 0x1e0, 0x160, however probing
|
||
of individual ports can be disabled by setting the
|
||
corresponding bits in the mask to 1. Bit 0 is for
|
||
the first port in the list above (0x1f0), and so on.
|
||
By default all supported ports are probed.
|
||
|
||
pata_legacy.qdi= [HW,LIBATA]
|
||
Format: <int>
|
||
Set to non-zero to probe QDI controllers. By default
|
||
set to 1 if CONFIG_PATA_QDI_MODULE, 0 otherwise.
|
||
|
||
pata_legacy.winbond= [HW,LIBATA]
|
||
Format: <int>
|
||
Set to non-zero to probe Winbond controllers. Use
|
||
the standard I/O port (0x130) if 1, otherwise the
|
||
value given is the I/O port to use (typically 0x1b0).
|
||
By default set to 1 if CONFIG_PATA_WINBOND_VLB_MODULE,
|
||
0 otherwise.
|
||
|
||
pata_platform.pio_mask= [HW,LIBATA]
|
||
Format: <int>
|
||
Supported PIO mode mask. Set individual bits to allow
|
||
the use of the respective PIO modes. Bit 0 is for
|
||
mode 0, bit 1 is for mode 1, and so on. Mode 0 only
|
||
allowed by default.
|
||
|
||
pause_on_oops=<int>
|
||
Halt all CPUs after the first oops has been printed for
|
||
the specified number of seconds. This is to be used if
|
||
your oopses keep scrolling off the screen.
|
||
|
||
pcbit= [HW,ISDN]
|
||
|
||
pci=option[,option...] [PCI,EARLY] various PCI subsystem options.
|
||
|
||
Some options herein operate on a specific device
|
||
or a set of devices (<pci_dev>). These are
|
||
specified in one of the following formats:
|
||
|
||
[<domain>:]<bus>:<dev>.<func>[/<dev>.<func>]*
|
||
pci:<vendor>:<device>[:<subvendor>:<subdevice>]
|
||
|
||
Note: the first format specifies a PCI
|
||
bus/device/function address which may change
|
||
if new hardware is inserted, if motherboard
|
||
firmware changes, or due to changes caused
|
||
by other kernel parameters. If the
|
||
domain is left unspecified, it is
|
||
taken to be zero. Optionally, a path
|
||
to a device through multiple device/function
|
||
addresses can be specified after the base
|
||
address (this is more robust against
|
||
renumbering issues). The second format
|
||
selects devices using IDs from the
|
||
configuration space which may match multiple
|
||
devices in the system.
|
||
|
||
earlydump dump PCI config space before the kernel
|
||
changes anything
|
||
off [X86] don't probe for the PCI bus
|
||
bios [X86-32] force use of PCI BIOS, don't access
|
||
the hardware directly. Use this if your machine
|
||
has a non-standard PCI host bridge.
|
||
nobios [X86-32] disallow use of PCI BIOS, only direct
|
||
hardware access methods are allowed. Use this
|
||
if you experience crashes upon bootup and you
|
||
suspect they are caused by the BIOS.
|
||
conf1 [X86] Force use of PCI Configuration Access
|
||
Mechanism 1 (config address in IO port 0xCF8,
|
||
data in IO port 0xCFC, both 32-bit).
|
||
conf2 [X86] Force use of PCI Configuration Access
|
||
Mechanism 2 (IO port 0xCF8 is an 8-bit port for
|
||
the function, IO port 0xCFA, also 8-bit, sets
|
||
bus number. The config space is then accessed
|
||
through ports 0xC000-0xCFFF).
|
||
See http://wiki.osdev.org/PCI for more info
|
||
on the configuration access mechanisms.
|
||
noaer [PCIE] If the PCIEAER kernel config parameter is
|
||
enabled, this kernel boot option can be used to
|
||
disable the use of PCIE advanced error reporting.
|
||
nodomains [PCI] Disable support for multiple PCI
|
||
root domains (aka PCI segments, in ACPI-speak).
|
||
nommconf [X86] Disable use of MMCONFIG for PCI
|
||
Configuration
|
||
check_enable_amd_mmconf [X86] check for and enable
|
||
properly configured MMIO access to PCI
|
||
config space on AMD family 10h CPU
|
||
nomsi [MSI] If the PCI_MSI kernel config parameter is
|
||
enabled, this kernel boot option can be used to
|
||
disable the use of MSI interrupts system-wide.
|
||
noioapicquirk [APIC] Disable all boot interrupt quirks.
|
||
Safety option to keep boot IRQs enabled. This
|
||
should never be necessary.
|
||
ioapicreroute [APIC] Enable rerouting of boot IRQs to the
|
||
primary IO-APIC for bridges that cannot disable
|
||
boot IRQs. This fixes a source of spurious IRQs
|
||
when the system masks IRQs.
|
||
noioapicreroute [APIC] Disable workaround that uses the
|
||
boot IRQ equivalent of an IRQ that connects to
|
||
a chipset where boot IRQs cannot be disabled.
|
||
The opposite of ioapicreroute.
|
||
biosirq [X86-32] Use PCI BIOS calls to get the interrupt
|
||
routing table. These calls are known to be buggy
|
||
on several machines and they hang the machine
|
||
when used, but on other computers it's the only
|
||
way to get the interrupt routing table. Try
|
||
this option if the kernel is unable to allocate
|
||
IRQs or discover secondary PCI buses on your
|
||
motherboard.
|
||
rom [X86] Assign address space to expansion ROMs.
|
||
Use with caution as certain devices share
|
||
address decoders between ROMs and other
|
||
resources.
|
||
norom [X86] Do not assign address space to
|
||
expansion ROMs that do not already have
|
||
BIOS assigned address ranges.
|
||
nobar [X86] Do not assign address space to the
|
||
BARs that weren't assigned by the BIOS.
|
||
irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
|
||
assigned automatically to PCI devices. You can
|
||
make the kernel exclude IRQs of your ISA cards
|
||
this way.
|
||
pirqaddr=0xAAAAA [X86] Specify the physical address
|
||
of the PIRQ table (normally generated
|
||
by the BIOS) if it is outside the
|
||
F0000h-100000h range.
|
||
lastbus=N [X86] Scan all buses thru bus #N. Can be
|
||
useful if the kernel is unable to find your
|
||
secondary buses and you want to tell it
|
||
explicitly which ones they are.
|
||
assign-busses [X86] Always assign all PCI bus
|
||
numbers ourselves, overriding
|
||
whatever the firmware may have done.
|
||
usepirqmask [X86] Honor the possible IRQ mask stored
|
||
in the BIOS $PIR table. This is needed on
|
||
some systems with broken BIOSes, notably
|
||
some HP Pavilion N5400 and Omnibook XE3
|
||
notebooks. This will have no effect if ACPI
|
||
IRQ routing is enabled.
|
||
noacpi [X86] Do not use ACPI for IRQ routing
|
||
or for PCI scanning.
|
||
use_crs [X86] Use PCI host bridge window information
|
||
from ACPI. On BIOSes from 2008 or later, this
|
||
is enabled by default. If you need to use this,
|
||
please report a bug.
|
||
nocrs [X86] Ignore PCI host bridge windows from ACPI.
|
||
If you need to use this, please report a bug.
|
||
use_e820 [X86] Use E820 reservations to exclude parts of
|
||
PCI host bridge windows. This is a workaround
|
||
for BIOS defects in host bridge _CRS methods.
|
||
If you need to use this, please report a bug to
|
||
<linux-pci@vger.kernel.org>.
|
||
no_e820 [X86] Ignore E820 reservations for PCI host
|
||
bridge windows. This is the default on modern
|
||
hardware. If you need to use this, please report
|
||
a bug to <linux-pci@vger.kernel.org>.
|
||
routeirq Do IRQ routing for all PCI devices.
|
||
This is normally done in pci_enable_device(),
|
||
so this option is a temporary workaround
|
||
for broken drivers that don't call it.
|
||
skip_isa_align [X86] do not align io start addr, so can
|
||
handle more pci cards
|
||
noearly [X86] Don't do any early type 1 scanning.
|
||
This might help on some broken boards which
|
||
machine check when some devices' config space
|
||
is read. But various workarounds are disabled
|
||
and some IOMMU drivers will not work.
|
||
bfsort Sort PCI devices into breadth-first order.
|
||
This sorting is done to get a device
|
||
order compatible with older (<= 2.4) kernels.
|
||
nobfsort Don't sort PCI devices into breadth-first order.
|
||
pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
|
||
tuning and use the BIOS-configured MPS defaults.
|
||
pcie_bus_safe Set every device's MPS to the largest value
|
||
supported by all devices below the root complex.
|
||
pcie_bus_perf Set device MPS to the largest allowable MPS
|
||
based on its parent bus. Also set MRRS (Max
|
||
Read Request Size) to the largest supported
|
||
value (no larger than the MPS that the device
|
||
or bus can support) for best performance.
|
||
pcie_bus_peer2peer Set every device's MPS to 128B, which
|
||
every device is guaranteed to support. This
|
||
configuration allows peer-to-peer DMA between
|
||
any pair of devices, possibly at the cost of
|
||
reduced performance. This also guarantees
|
||
that hot-added devices will work.
|
||
cbiosize=nn[KMG] The fixed amount of bus space which is
|
||
reserved for the CardBus bridge's IO window.
|
||
The default value is 256 bytes.
|
||
cbmemsize=nn[KMG] The fixed amount of bus space which is
|
||
reserved for the CardBus bridge's memory
|
||
window. The default value is 64 megabytes.
|
||
resource_alignment=
|
||
Format:
|
||
[<order of align>@]<pci_dev>[; ...]
|
||
Specifies alignment and device to reassign
|
||
aligned memory resources. How to
|
||
specify the device is described above.
|
||
If <order of align> is not specified,
|
||
PAGE_SIZE is used as alignment.
|
||
A PCI-PCI bridge can be specified if resource
|
||
windows need to be expanded.
|
||
To specify the alignment for several
|
||
instances of a device, the PCI vendor,
|
||
device, subvendor, and subdevice may be
|
||
specified, e.g., 12@pci:8086:9c22:103c:198f
|
||
for 4096-byte alignment.
|
||
ecrc= Enable/disable PCIe ECRC (transaction layer
|
||
end-to-end CRC checking). Only effective if
|
||
OS has native AER control (either granted by
|
||
ACPI _OSC or forced via "pcie_ports=native")
|
||
bios: Use BIOS/firmware settings. This is the
|
||
the default.
|
||
off: Turn ECRC off
|
||
on: Turn ECRC on.
|
||
hpiosize=nn[KMG] The fixed amount of bus space which is
|
||
reserved for hotplug bridge's IO window.
|
||
Default size is 256 bytes.
|
||
hpmmiosize=nn[KMG] The fixed amount of bus space which is
|
||
reserved for hotplug bridge's MMIO window.
|
||
Default size is 2 megabytes.
|
||
hpmmioprefsize=nn[KMG] The fixed amount of bus space which is
|
||
reserved for hotplug bridge's MMIO_PREF window.
|
||
Default size is 2 megabytes.
|
||
hpmemsize=nn[KMG] The fixed amount of bus space which is
|
||
reserved for hotplug bridge's MMIO and
|
||
MMIO_PREF window.
|
||
Default size is 2 megabytes.
|
||
hpbussize=nn The minimum amount of additional bus numbers
|
||
reserved for buses below a hotplug bridge.
|
||
Default is 1.
|
||
realloc= Enable/disable reallocating PCI bridge resources
|
||
if allocations done by BIOS are too small to
|
||
accommodate resources required by all child
|
||
devices.
|
||
off: Turn realloc off
|
||
on: Turn realloc on
|
||
realloc same as realloc=on
|
||
noari do not use PCIe ARI.
|
||
noats [PCIE, Intel-IOMMU, AMD-IOMMU]
|
||
do not use PCIe ATS (and IOMMU device IOTLB).
|
||
pcie_scan_all Scan all possible PCIe devices. Otherwise we
|
||
only look for one device below a PCIe downstream
|
||
port.
|
||
big_root_window Try to add a big 64bit memory window to the PCIe
|
||
root complex on AMD CPUs. Some GFX hardware
|
||
can resize a BAR to allow access to all VRAM.
|
||
Adding the window is slightly risky (it may
|
||
conflict with unreported devices), so this
|
||
taints the kernel.
|
||
disable_acs_redir=<pci_dev>[; ...]
|
||
Specify one or more PCI devices (in the format
|
||
specified above) separated by semicolons.
|
||
Each device specified will have the PCI ACS
|
||
redirect capabilities forced off which will
|
||
allow P2P traffic between devices through
|
||
bridges without forcing it upstream. Note:
|
||
this removes isolation between devices and
|
||
may put more devices in an IOMMU group.
|
||
config_acs=
|
||
Format:
|
||
<ACS flags>@<pci_dev>[; ...]
|
||
Specify one or more PCI devices (in the format
|
||
specified above) optionally prepended with flags
|
||
and separated by semicolons. The respective
|
||
capabilities will be enabled, disabled or
|
||
unchanged based on what is specified in
|
||
flags.
|
||
|
||
ACS Flags is defined as follows:
|
||
bit-0 : ACS Source Validation
|
||
bit-1 : ACS Translation Blocking
|
||
bit-2 : ACS P2P Request Redirect
|
||
bit-3 : ACS P2P Completion Redirect
|
||
bit-4 : ACS Upstream Forwarding
|
||
bit-5 : ACS P2P Egress Control
|
||
bit-6 : ACS Direct Translated P2P
|
||
Each bit can be marked as:
|
||
'0' – force disabled
|
||
'1' – force enabled
|
||
'x' – unchanged
|
||
For example,
|
||
pci=config_acs=10x
|
||
would configure all devices that support
|
||
ACS to enable P2P Request Redirect, disable
|
||
Translation Blocking, and leave Source
|
||
Validation unchanged from whatever power-up
|
||
or firmware set it to.
|
||
|
||
Note: this may remove isolation between devices
|
||
and may put more devices in an IOMMU group.
|
||
force_floating [S390] Force usage of floating interrupts.
|
||
nomio [S390] Do not use MIO instructions.
|
||
norid [S390] ignore the RID field and force use of
|
||
one PCI domain per PCI function
|
||
|
||
pcie_aspm= [PCIE] Forcibly enable or ignore PCIe Active State Power
|
||
Management.
|
||
off Don't touch ASPM configuration at all. Leave any
|
||
configuration done by firmware unchanged.
|
||
force Enable ASPM even on devices that claim not to support it.
|
||
WARNING: Forcing ASPM on may cause system lockups.
|
||
|
||
pcie_ports= [PCIE] PCIe port services handling:
|
||
native Use native PCIe services (PME, AER, DPC, PCIe hotplug)
|
||
even if the platform doesn't give the OS permission to
|
||
use them. This may cause conflicts if the platform
|
||
also tries to use these services.
|
||
dpc-native Use native PCIe service for DPC only. May
|
||
cause conflicts if firmware uses AER or DPC.
|
||
compat Disable native PCIe services (PME, AER, DPC, PCIe
|
||
hotplug).
|
||
|
||
pcie_port_pm= [PCIE] PCIe port power management handling:
|
||
off Disable power management of all PCIe ports
|
||
force Forcibly enable power management of all PCIe ports
|
||
|
||
pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
|
||
nomsi Do not use MSI for native PCIe PME signaling (this makes
|
||
all PCIe root ports use INTx for all services).
|
||
|
||
pcmv= [HW,PCMCIA] BadgePAD 4
|
||
|
||
pd_ignore_unused
|
||
[PM]
|
||
Keep all power-domains already enabled by bootloader on,
|
||
even if no driver has claimed them. This is useful
|
||
for debug and development, but should not be
|
||
needed on a platform with proper driver support.
|
||
|
||
pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
|
||
boot time.
|
||
Format: { 0 | 1 }
|
||
See arch/parisc/kernel/pdc_chassis.c
|
||
|
||
percpu_alloc= [MM,EARLY]
|
||
Select which percpu first chunk allocator to use.
|
||
Currently supported values are "embed" and "page".
|
||
Archs may support subset or none of the selections.
|
||
See comments in mm/percpu.c for details on each
|
||
allocator. This parameter is primarily for debugging
|
||
and performance comparison.
|
||
|
||
pirq= [SMP,APIC] Manual mp-table setup
|
||
See Documentation/arch/x86/i386/IO-APIC.rst.
|
||
|
||
plip= [PPT,NET] Parallel port network link
|
||
Format: { parport<nr> | timid | 0 }
|
||
See also Documentation/admin-guide/parport.rst.
|
||
|
||
pmtmr= [X86] Manual setup of pmtmr I/O Port.
|
||
Override pmtimer IOPort with a hex value.
|
||
e.g. pmtmr=0x508
|
||
|
||
pmu_override= [PPC] Override the PMU.
|
||
This option takes over the PMU facility, so it is no
|
||
longer usable by perf. Setting this option starts the
|
||
PMU counters by setting MMCR0 to 0 (the FC bit is
|
||
cleared). If a number is given, then MMCR1 is set to
|
||
that number, otherwise (e.g., 'pmu_override=on'), MMCR1
|
||
remains 0.
|
||
|
||
pm_debug_messages [SUSPEND,KNL]
|
||
Enable suspend/resume debug messages during boot up.
|
||
|
||
pnp.debug=1 [PNP]
|
||
Enable PNP debug messages (depends on the
|
||
CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
|
||
via /sys/module/pnp/parameters/debug. We always show
|
||
current resource usage; turning this on also shows
|
||
possible settings and some assignment information.
|
||
|
||
pnpacpi= [ACPI]
|
||
{ off }
|
||
|
||
pnpbios= [ISAPNP]
|
||
{ on | off | curr | res | no-curr | no-res }
|
||
|
||
pnp_reserve_irq=
|
||
[ISAPNP] Exclude IRQs for the autoconfiguration
|
||
|
||
pnp_reserve_dma=
|
||
[ISAPNP] Exclude DMAs for the autoconfiguration
|
||
|
||
pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
|
||
Ranges are in pairs (I/O port base and size).
|
||
|
||
pnp_reserve_mem=
|
||
[ISAPNP] Exclude memory regions for the
|
||
autoconfiguration.
|
||
Ranges are in pairs (memory base and size).
|
||
|
||
ports= [IP_VS_FTP] IPVS ftp helper module
|
||
Default is 21.
|
||
Up to 8 (IP_VS_APP_MAX_PORTS) ports
|
||
may be specified.
|
||
Format: <port>,<port>....
|
||
|
||
possible_cpus= [SMP,S390,X86]
|
||
Format: <unsigned int>
|
||
Set the number of possible CPUs, overriding the
|
||
regular discovery mechanisms (such as ACPI/FW, etc).
|
||
|
||
powersave=off [PPC] This option disables power saving features.
|
||
It specifically disables cpuidle and sets the
|
||
platform machine description specific power_save
|
||
function to NULL. On Idle the CPU just reduces
|
||
execution priority.
|
||
|
||
ppc_strict_facility_enable
|
||
[PPC,ENABLE] This option catches any kernel floating point,
|
||
Altivec, VSX and SPE outside of regions specifically
|
||
allowed (eg kernel_enable_fpu()/kernel_disable_fpu()).
|
||
There is some performance impact when enabling this.
|
||
|
||
ppc_tm= [PPC,EARLY]
|
||
Format: {"off"}
|
||
Disable Hardware Transactional Memory
|
||
|
||
preempt= [KNL]
|
||
Select preemption mode if you have CONFIG_PREEMPT_DYNAMIC
|
||
none - Limited to cond_resched() calls
|
||
voluntary - Limited to cond_resched() and might_sleep() calls
|
||
full - Any section that isn't explicitly preempt disabled
|
||
can be preempted anytime. Tasks will also yield
|
||
contended spinlocks (if the critical section isn't
|
||
explicitly preempt disabled beyond the lock itself).
|
||
|
||
print-fatal-signals=
|
||
[KNL] debug: print fatal signals
|
||
|
||
If enabled, warn about various signal handling
|
||
related application anomalies: too many signals,
|
||
too many POSIX.1 timers, fatal signals causing a
|
||
coredump - etc.
|
||
|
||
If you hit the warning due to signal overflow,
|
||
you might want to try "ulimit -i unlimited".
|
||
|
||
default: off.
|
||
|
||
printk.always_kmsg_dump=
|
||
Trigger kmsg_dump for cases other than kernel oops or
|
||
panics
|
||
Format: <bool> (1/Y/y=enable, 0/N/n=disable)
|
||
default: disabled
|
||
|
||
printk.console_no_auto_verbose=
|
||
Disable console loglevel raise on oops, panic
|
||
or lockdep-detected issues (only if lock debug is on).
|
||
With an exception to setups with low baudrate on
|
||
serial console, keeping this 0 is a good choice
|
||
in order to provide more debug information.
|
||
Format: <bool>
|
||
default: 0 (auto_verbose is enabled)
|
||
|
||
printk.devkmsg={on,off,ratelimit}
|
||
Control writing to /dev/kmsg.
|
||
on - unlimited logging to /dev/kmsg from userspace
|
||
off - logging to /dev/kmsg disabled
|
||
ratelimit - ratelimit the logging
|
||
Default: ratelimit
|
||
|
||
printk.time= Show timing data prefixed to each printk message line
|
||
Format: <bool> (1/Y/y=enable, 0/N/n=disable)
|
||
|
||
proc_mem.force_override= [KNL]
|
||
Format: {always | ptrace | never}
|
||
Traditionally /proc/pid/mem allows memory permissions to be
|
||
overridden without restrictions. This option may be set to
|
||
restrict that. Can be one of:
|
||
- 'always': traditional behavior always allows mem overrides.
|
||
- 'ptrace': only allow mem overrides for active ptracers.
|
||
- 'never': never allow mem overrides.
|
||
If not specified, default is the CONFIG_PROC_MEM_* choice.
|
||
|
||
processor.max_cstate= [HW,ACPI]
|
||
Limit processor to maximum C-state
|
||
max_cstate=9 overrides any DMI blacklist limit.
|
||
|
||
processor.nocst [HW,ACPI]
|
||
Ignore the _CST method to determine C-states,
|
||
instead using the legacy FADT method
|
||
|
||
profile= [KNL] Enable kernel profiling via /proc/profile
|
||
Format: [<profiletype>,]<number>
|
||
Param: <profiletype>: "schedule" or "kvm"
|
||
[defaults to kernel profiling]
|
||
Param: "schedule" - profile schedule points.
|
||
Param: "kvm" - profile VM exits.
|
||
Param: <number> - step/bucket size as a power of 2 for
|
||
statistical time based profiling.
|
||
|
||
prompt_ramdisk= [RAM] [Deprecated]
|
||
|
||
prot_virt= [S390] enable hosting protected virtual machines
|
||
isolated from the hypervisor (if hardware supports
|
||
that). If enabled, the default kernel base address
|
||
might be overridden even when Kernel Address Space
|
||
Layout Randomization is disabled.
|
||
Format: <bool>
|
||
|
||
psi= [KNL] Enable or disable pressure stall information
|
||
tracking.
|
||
Format: <bool>
|
||
|
||
psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
|
||
probe for; one of (bare|imps|exps|lifebook|any).
|
||
psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
|
||
per second.
|
||
psmouse.resetafter= [HW,MOUSE]
|
||
Try to reset the device after so many bad packets
|
||
(0 = never).
|
||
psmouse.resolution=
|
||
[HW,MOUSE] Set desired mouse resolution, in dpi.
|
||
psmouse.smartscroll=
|
||
[HW,MOUSE] Controls Logitech smartscroll autorepeat.
|
||
0 = disabled, 1 = enabled (default).
|
||
|
||
pstore.backend= Specify the name of the pstore backend to use
|
||
|
||
pti= [X86-64] Control Page Table Isolation of user and
|
||
kernel address spaces. Disabling this feature
|
||
removes hardening, but improves performance of
|
||
system calls and interrupts.
|
||
|
||
on - unconditionally enable
|
||
off - unconditionally disable
|
||
auto - kernel detects whether your CPU model is
|
||
vulnerable to issues that PTI mitigates
|
||
|
||
Not specifying this option is equivalent to pti=auto.
|
||
|
||
pty.legacy_count=
|
||
[KNL] Number of legacy pty's. Overwrites compiled-in
|
||
default number.
|
||
|
||
quiet [KNL,EARLY] Disable most log messages
|
||
|
||
r128= [HW,DRM]
|
||
|
||
radix_hcall_invalidate=on [PPC/PSERIES]
|
||
Disable RADIX GTSE feature and use hcall for TLB
|
||
invalidate.
|
||
|
||
raid= [HW,RAID]
|
||
See Documentation/admin-guide/md.rst.
|
||
|
||
ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
|
||
See Documentation/admin-guide/blockdev/ramdisk.rst.
|
||
|
||
ramdisk_start= [RAM] RAM disk image start address
|
||
|
||
random.trust_cpu=off
|
||
[KNL,EARLY] Disable trusting the use of the CPU's
|
||
random number generator (if available) to
|
||
initialize the kernel's RNG.
|
||
|
||
random.trust_bootloader=off
|
||
[KNL,EARLY] Disable trusting the use of the a seed
|
||
passed by the bootloader (if available) to
|
||
initialize the kernel's RNG.
|
||
|
||
randomize_kstack_offset=
|
||
[KNL,EARLY] Enable or disable kernel stack offset
|
||
randomization, which provides roughly 5 bits of
|
||
entropy, frustrating memory corruption attacks
|
||
that depend on stack address determinism or
|
||
cross-syscall address exposures. This is only
|
||
available on architectures that have defined
|
||
CONFIG_HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET.
|
||
Format: <bool> (1/Y/y=enable, 0/N/n=disable)
|
||
Default is CONFIG_RANDOMIZE_KSTACK_OFFSET_DEFAULT.
|
||
|
||
ras=option[,option,...] [KNL] RAS-specific options
|
||
|
||
cec_disable [X86]
|
||
Disable the Correctable Errors Collector,
|
||
see CONFIG_RAS_CEC help text.
|
||
|
||
rcu_nocbs[=cpu-list]
|
||
[KNL] The optional argument is a cpu list,
|
||
as described above.
|
||
|
||
In kernels built with CONFIG_RCU_NOCB_CPU=y,
|
||
enable the no-callback CPU mode, which prevents
|
||
such CPUs' callbacks from being invoked in
|
||
softirq context. Invocation of such CPUs' RCU
|
||
callbacks will instead be offloaded to "rcuox/N"
|
||
kthreads created for that purpose, where "x" is
|
||
"p" for RCU-preempt, "s" for RCU-sched, and "g"
|
||
for the kthreads that mediate grace periods; and
|
||
"N" is the CPU number. This reduces OS jitter on
|
||
the offloaded CPUs, which can be useful for HPC
|
||
and real-time workloads. It can also improve
|
||
energy efficiency for asymmetric multiprocessors.
|
||
|
||
If a cpulist is passed as an argument, the specified
|
||
list of CPUs is set to no-callback mode from boot.
|
||
|
||
Otherwise, if the '=' sign and the cpulist
|
||
arguments are omitted, no CPU will be set to
|
||
no-callback mode from boot but the mode may be
|
||
toggled at runtime via cpusets.
|
||
|
||
Note that this argument takes precedence over
|
||
the CONFIG_RCU_NOCB_CPU_DEFAULT_ALL option.
|
||
|
||
rcu_nocb_poll [KNL]
|
||
Rather than requiring that offloaded CPUs
|
||
(specified by rcu_nocbs= above) explicitly
|
||
awaken the corresponding "rcuoN" kthreads,
|
||
make these kthreads poll for callbacks.
|
||
This improves the real-time response for the
|
||
offloaded CPUs by relieving them of the need to
|
||
wake up the corresponding kthread, but degrades
|
||
energy efficiency by requiring that the kthreads
|
||
periodically wake up to do the polling.
|
||
|
||
rcutree.blimit= [KNL]
|
||
Set maximum number of finished RCU callbacks to
|
||
process in one batch.
|
||
|
||
rcutree.csd_lock_suppress_rcu_stall= [KNL]
|
||
Do only a one-line RCU CPU stall warning when
|
||
there is an ongoing too-long CSD-lock wait.
|
||
|
||
rcutree.do_rcu_barrier= [KNL]
|
||
Request a call to rcu_barrier(). This is
|
||
throttled so that userspace tests can safely
|
||
hammer on the sysfs variable if they so choose.
|
||
If triggered before the RCU grace-period machinery
|
||
is fully active, this will error out with EAGAIN.
|
||
|
||
rcutree.dump_tree= [KNL]
|
||
Dump the structure of the rcu_node combining tree
|
||
out at early boot. This is used for diagnostic
|
||
purposes, to verify correct tree setup.
|
||
|
||
rcutree.gp_cleanup_delay= [KNL]
|
||
Set the number of jiffies to delay each step of
|
||
RCU grace-period cleanup.
|
||
|
||
rcutree.gp_init_delay= [KNL]
|
||
Set the number of jiffies to delay each step of
|
||
RCU grace-period initialization.
|
||
|
||
rcutree.gp_preinit_delay= [KNL]
|
||
Set the number of jiffies to delay each step of
|
||
RCU grace-period pre-initialization, that is,
|
||
the propagation of recent CPU-hotplug changes up
|
||
the rcu_node combining tree.
|
||
|
||
rcutree.jiffies_till_first_fqs= [KNL]
|
||
Set delay from grace-period initialization to
|
||
first attempt to force quiescent states.
|
||
Units are jiffies, minimum value is zero,
|
||
and maximum value is HZ.
|
||
|
||
rcutree.jiffies_till_next_fqs= [KNL]
|
||
Set delay between subsequent attempts to force
|
||
quiescent states. Units are jiffies, minimum
|
||
value is one, and maximum value is HZ.
|
||
|
||
rcutree.jiffies_till_sched_qs= [KNL]
|
||
Set required age in jiffies for a
|
||
given grace period before RCU starts
|
||
soliciting quiescent-state help from
|
||
rcu_note_context_switch() and cond_resched().
|
||
If not specified, the kernel will calculate
|
||
a value based on the most recent settings
|
||
of rcutree.jiffies_till_first_fqs
|
||
and rcutree.jiffies_till_next_fqs.
|
||
This calculated value may be viewed in
|
||
rcutree.jiffies_to_sched_qs. Any attempt to set
|
||
rcutree.jiffies_to_sched_qs will be cheerfully
|
||
overwritten.
|
||
|
||
rcutree.kthread_prio= [KNL,BOOT]
|
||
Set the SCHED_FIFO priority of the RCU per-CPU
|
||
kthreads (rcuc/N). This value is also used for
|
||
the priority of the RCU boost threads (rcub/N)
|
||
and for the RCU grace-period kthreads (rcu_bh,
|
||
rcu_preempt, and rcu_sched). If RCU_BOOST is
|
||
set, valid values are 1-99 and the default is 1
|
||
(the least-favored priority). Otherwise, when
|
||
RCU_BOOST is not set, valid values are 0-99 and
|
||
the default is zero (non-realtime operation).
|
||
When RCU_NOCB_CPU is set, also adjust the
|
||
priority of NOCB callback kthreads.
|
||
|
||
rcutree.nocb_nobypass_lim_per_jiffy= [KNL]
|
||
On callback-offloaded (rcu_nocbs) CPUs,
|
||
RCU reduces the lock contention that would
|
||
otherwise be caused by callback floods through
|
||
use of the ->nocb_bypass list. However, in the
|
||
common non-flooded case, RCU queues directly to
|
||
the main ->cblist in order to avoid the extra
|
||
overhead of the ->nocb_bypass list and its lock.
|
||
But if there are too many callbacks queued during
|
||
a single jiffy, RCU pre-queues the callbacks into
|
||
the ->nocb_bypass queue. The definition of "too
|
||
many" is supplied by this kernel boot parameter.
|
||
|
||
rcutree.nohz_full_patience_delay= [KNL]
|
||
On callback-offloaded (rcu_nocbs) CPUs, avoid
|
||
disturbing RCU unless the grace period has
|
||
reached the specified age in milliseconds.
|
||
Defaults to zero. Large values will be capped
|
||
at five seconds. All values will be rounded down
|
||
to the nearest value representable by jiffies.
|
||
|
||
rcutree.qhimark= [KNL]
|
||
Set threshold of queued RCU callbacks beyond which
|
||
batch limiting is disabled.
|
||
|
||
rcutree.qlowmark= [KNL]
|
||
Set threshold of queued RCU callbacks below which
|
||
batch limiting is re-enabled.
|
||
|
||
rcutree.qovld= [KNL]
|
||
Set threshold of queued RCU callbacks beyond which
|
||
RCU's force-quiescent-state scan will aggressively
|
||
enlist help from cond_resched() and sched IPIs to
|
||
help CPUs more quickly reach quiescent states.
|
||
Set to less than zero to make this be set based
|
||
on rcutree.qhimark at boot time and to zero to
|
||
disable more aggressive help enlistment.
|
||
|
||
rcutree.rcu_delay_page_cache_fill_msec= [KNL]
|
||
Set the page-cache refill delay (in milliseconds)
|
||
in response to low-memory conditions. The range
|
||
of permitted values is in the range 0:100000.
|
||
|
||
rcutree.rcu_divisor= [KNL]
|
||
Set the shift-right count to use to compute
|
||
the callback-invocation batch limit bl from
|
||
the number of callbacks queued on this CPU.
|
||
The result will be bounded below by the value of
|
||
the rcutree.blimit kernel parameter. Every bl
|
||
callbacks, the softirq handler will exit in
|
||
order to allow the CPU to do other work.
|
||
|
||
Please note that this callback-invocation batch
|
||
limit applies only to non-offloaded callback
|
||
invocation. Offloaded callbacks are instead
|
||
invoked in the context of an rcuoc kthread, which
|
||
scheduler will preempt as it does any other task.
|
||
|
||
rcutree.rcu_fanout_exact= [KNL]
|
||
Disable autobalancing of the rcu_node combining
|
||
tree. This is used by rcutorture, and might
|
||
possibly be useful for architectures having high
|
||
cache-to-cache transfer latencies.
|
||
|
||
rcutree.rcu_fanout_leaf= [KNL]
|
||
Change the number of CPUs assigned to each
|
||
leaf rcu_node structure. Useful for very
|
||
large systems, which will choose the value 64,
|
||
and for NUMA systems with large remote-access
|
||
latencies, which will choose a value aligned
|
||
with the appropriate hardware boundaries.
|
||
|
||
rcutree.rcu_min_cached_objs= [KNL]
|
||
Minimum number of objects which are cached and
|
||
maintained per one CPU. Object size is equal
|
||
to PAGE_SIZE. The cache allows to reduce the
|
||
pressure to page allocator, also it makes the
|
||
whole algorithm to behave better in low memory
|
||
condition.
|
||
|
||
rcutree.rcu_nocb_gp_stride= [KNL]
|
||
Set the number of NOCB callback kthreads in
|
||
each group, which defaults to the square root
|
||
of the number of CPUs. Larger numbers reduce
|
||
the wakeup overhead on the global grace-period
|
||
kthread, but increases that same overhead on
|
||
each group's NOCB grace-period kthread.
|
||
|
||
rcutree.rcu_kick_kthreads= [KNL]
|
||
Cause the grace-period kthread to get an extra
|
||
wake_up() if it sleeps three times longer than
|
||
it should at force-quiescent-state time.
|
||
This wake_up() will be accompanied by a
|
||
WARN_ONCE() splat and an ftrace_dump().
|
||
|
||
rcutree.rcu_resched_ns= [KNL]
|
||
Limit the time spend invoking a batch of RCU
|
||
callbacks to the specified number of nanoseconds.
|
||
By default, this limit is checked only once
|
||
every 32 callbacks in order to limit the pain
|
||
inflicted by local_clock() overhead.
|
||
|
||
rcutree.rcu_unlock_delay= [KNL]
|
||
In CONFIG_RCU_STRICT_GRACE_PERIOD=y kernels,
|
||
this specifies an rcu_read_unlock()-time delay
|
||
in microseconds. This defaults to zero.
|
||
Larger delays increase the probability of
|
||
catching RCU pointer leaks, that is, buggy use
|
||
of RCU-protected pointers after the relevant
|
||
rcu_read_unlock() has completed.
|
||
|
||
rcutree.sysrq_rcu= [KNL]
|
||
Commandeer a sysrq key to dump out Tree RCU's
|
||
rcu_node tree with an eye towards determining
|
||
why a new grace period has not yet started.
|
||
|
||
rcutree.use_softirq= [KNL]
|
||
If set to zero, move all RCU_SOFTIRQ processing to
|
||
per-CPU rcuc kthreads. Defaults to a non-zero
|
||
value, meaning that RCU_SOFTIRQ is used by default.
|
||
Specify rcutree.use_softirq=0 to use rcuc kthreads.
|
||
|
||
But note that CONFIG_PREEMPT_RT=y kernels disable
|
||
this kernel boot parameter, forcibly setting it
|
||
to zero.
|
||
|
||
rcutree.enable_rcu_lazy= [KNL]
|
||
To save power, batch RCU callbacks and flush after
|
||
delay, memory pressure or callback list growing too
|
||
big.
|
||
|
||
rcutree.rcu_normal_wake_from_gp= [KNL]
|
||
Reduces a latency of synchronize_rcu() call. This approach
|
||
maintains its own track of synchronize_rcu() callers, so it
|
||
does not interact with regular callbacks because it does not
|
||
use a call_rcu[_hurry]() path. Please note, this is for a
|
||
normal grace period.
|
||
|
||
How to enable it:
|
||
|
||
echo 1 > /sys/module/rcutree/parameters/rcu_normal_wake_from_gp
|
||
or pass a boot parameter "rcutree.rcu_normal_wake_from_gp=1"
|
||
|
||
Default is 0.
|
||
|
||
rcuscale.gp_async= [KNL]
|
||
Measure performance of asynchronous
|
||
grace-period primitives such as call_rcu().
|
||
|
||
rcuscale.gp_async_max= [KNL]
|
||
Specify the maximum number of outstanding
|
||
callbacks per writer thread. When a writer
|
||
thread exceeds this limit, it invokes the
|
||
corresponding flavor of rcu_barrier() to allow
|
||
previously posted callbacks to drain.
|
||
|
||
rcuscale.gp_exp= [KNL]
|
||
Measure performance of expedited synchronous
|
||
grace-period primitives.
|
||
|
||
rcuscale.holdoff= [KNL]
|
||
Set test-start holdoff period. The purpose of
|
||
this parameter is to delay the start of the
|
||
test until boot completes in order to avoid
|
||
interference.
|
||
|
||
rcuscale.kfree_by_call_rcu= [KNL]
|
||
In kernels built with CONFIG_RCU_LAZY=y, test
|
||
call_rcu() instead of kfree_rcu().
|
||
|
||
rcuscale.kfree_mult= [KNL]
|
||
Instead of allocating an object of size kfree_obj,
|
||
allocate one of kfree_mult * sizeof(kfree_obj).
|
||
Defaults to 1.
|
||
|
||
rcuscale.kfree_rcu_test= [KNL]
|
||
Set to measure performance of kfree_rcu() flooding.
|
||
|
||
rcuscale.kfree_rcu_test_double= [KNL]
|
||
Test the double-argument variant of kfree_rcu().
|
||
If this parameter has the same value as
|
||
rcuscale.kfree_rcu_test_single, both the single-
|
||
and double-argument variants are tested.
|
||
|
||
rcuscale.kfree_rcu_test_single= [KNL]
|
||
Test the single-argument variant of kfree_rcu().
|
||
If this parameter has the same value as
|
||
rcuscale.kfree_rcu_test_double, both the single-
|
||
and double-argument variants are tested.
|
||
|
||
rcuscale.kfree_nthreads= [KNL]
|
||
The number of threads running loops of kfree_rcu().
|
||
|
||
rcuscale.kfree_alloc_num= [KNL]
|
||
Number of allocations and frees done in an iteration.
|
||
|
||
rcuscale.kfree_loops= [KNL]
|
||
Number of loops doing rcuscale.kfree_alloc_num number
|
||
of allocations and frees.
|
||
|
||
rcuscale.minruntime= [KNL]
|
||
Set the minimum test run time in seconds. This
|
||
does not affect the data-collection interval,
|
||
but instead allows better measurement of things
|
||
like CPU consumption.
|
||
|
||
rcuscale.nreaders= [KNL]
|
||
Set number of RCU readers. The value -1 selects
|
||
N, where N is the number of CPUs. A value
|
||
"n" less than -1 selects N-n+1, where N is again
|
||
the number of CPUs. For example, -2 selects N
|
||
(the number of CPUs), -3 selects N+1, and so on.
|
||
A value of "n" less than or equal to -N selects
|
||
a single reader.
|
||
|
||
rcuscale.nwriters= [KNL]
|
||
Set number of RCU writers. The values operate
|
||
the same as for rcuscale.nreaders.
|
||
N, where N is the number of CPUs
|
||
|
||
rcuscale.scale_type= [KNL]
|
||
Specify the RCU implementation to test.
|
||
|
||
rcuscale.shutdown= [KNL]
|
||
Shut the system down after performance tests
|
||
complete. This is useful for hands-off automated
|
||
testing.
|
||
|
||
rcuscale.verbose= [KNL]
|
||
Enable additional printk() statements.
|
||
|
||
rcuscale.writer_holdoff= [KNL]
|
||
Write-side holdoff between grace periods,
|
||
in microseconds. The default of zero says
|
||
no holdoff.
|
||
|
||
rcuscale.writer_holdoff_jiffies= [KNL]
|
||
Additional write-side holdoff between grace
|
||
periods, but in jiffies. The default of zero
|
||
says no holdoff.
|
||
|
||
rcutorture.fqs_duration= [KNL]
|
||
Set duration of force_quiescent_state bursts
|
||
in microseconds.
|
||
|
||
rcutorture.fqs_holdoff= [KNL]
|
||
Set holdoff time within force_quiescent_state bursts
|
||
in microseconds.
|
||
|
||
rcutorture.fqs_stutter= [KNL]
|
||
Set wait time between force_quiescent_state bursts
|
||
in seconds.
|
||
|
||
rcutorture.fwd_progress= [KNL]
|
||
Specifies the number of kthreads to be used
|
||
for RCU grace-period forward-progress testing
|
||
for the types of RCU supporting this notion.
|
||
Defaults to 1 kthread, values less than zero or
|
||
greater than the number of CPUs cause the number
|
||
of CPUs to be used.
|
||
|
||
rcutorture.fwd_progress_div= [KNL]
|
||
Specify the fraction of a CPU-stall-warning
|
||
period to do tight-loop forward-progress testing.
|
||
|
||
rcutorture.fwd_progress_holdoff= [KNL]
|
||
Number of seconds to wait between successive
|
||
forward-progress tests.
|
||
|
||
rcutorture.fwd_progress_need_resched= [KNL]
|
||
Enclose cond_resched() calls within checks for
|
||
need_resched() during tight-loop forward-progress
|
||
testing.
|
||
|
||
rcutorture.gp_cond= [KNL]
|
||
Use conditional/asynchronous update-side
|
||
primitives, if available.
|
||
|
||
rcutorture.gp_exp= [KNL]
|
||
Use expedited update-side primitives, if available.
|
||
|
||
rcutorture.gp_normal= [KNL]
|
||
Use normal (non-expedited) asynchronous
|
||
update-side primitives, if available.
|
||
|
||
rcutorture.gp_sync= [KNL]
|
||
Use normal (non-expedited) synchronous
|
||
update-side primitives, if available. If all
|
||
of rcutorture.gp_cond=, rcutorture.gp_exp=,
|
||
rcutorture.gp_normal=, and rcutorture.gp_sync=
|
||
are zero, rcutorture acts as if is interpreted
|
||
they are all non-zero.
|
||
|
||
rcutorture.irqreader= [KNL]
|
||
Run RCU readers from irq handlers, or, more
|
||
accurately, from a timer handler. Not all RCU
|
||
flavors take kindly to this sort of thing.
|
||
|
||
rcutorture.leakpointer= [KNL]
|
||
Leak an RCU-protected pointer out of the reader.
|
||
This can of course result in splats, and is
|
||
intended to test the ability of things like
|
||
CONFIG_RCU_STRICT_GRACE_PERIOD=y to detect
|
||
such leaks.
|
||
|
||
rcutorture.n_barrier_cbs= [KNL]
|
||
Set callbacks/threads for rcu_barrier() testing.
|
||
|
||
rcutorture.nfakewriters= [KNL]
|
||
Set number of concurrent RCU writers. These just
|
||
stress RCU, they don't participate in the actual
|
||
test, hence the "fake".
|
||
|
||
rcutorture.nocbs_nthreads= [KNL]
|
||
Set number of RCU callback-offload togglers.
|
||
Zero (the default) disables toggling.
|
||
|
||
rcutorture.nocbs_toggle= [KNL]
|
||
Set the delay in milliseconds between successive
|
||
callback-offload toggling attempts.
|
||
|
||
rcutorture.nreaders= [KNL]
|
||
Set number of RCU readers. The value -1 selects
|
||
N-1, where N is the number of CPUs. A value
|
||
"n" less than -1 selects N-n-2, where N is again
|
||
the number of CPUs. For example, -2 selects N
|
||
(the number of CPUs), -3 selects N+1, and so on.
|
||
|
||
rcutorture.object_debug= [KNL]
|
||
Enable debug-object double-call_rcu() testing.
|
||
|
||
rcutorture.onoff_holdoff= [KNL]
|
||
Set time (s) after boot for CPU-hotplug testing.
|
||
|
||
rcutorture.onoff_interval= [KNL]
|
||
Set time (jiffies) between CPU-hotplug operations,
|
||
or zero to disable CPU-hotplug testing.
|
||
|
||
rcutorture.read_exit= [KNL]
|
||
Set the number of read-then-exit kthreads used
|
||
to test the interaction of RCU updaters and
|
||
task-exit processing.
|
||
|
||
rcutorture.read_exit_burst= [KNL]
|
||
The number of times in a given read-then-exit
|
||
episode that a set of read-then-exit kthreads
|
||
is spawned.
|
||
|
||
rcutorture.read_exit_delay= [KNL]
|
||
The delay, in seconds, between successive
|
||
read-then-exit testing episodes.
|
||
|
||
rcutorture.shuffle_interval= [KNL]
|
||
Set task-shuffle interval (s). Shuffling tasks
|
||
allows some CPUs to go into dyntick-idle mode
|
||
during the rcutorture test.
|
||
|
||
rcutorture.shutdown_secs= [KNL]
|
||
Set time (s) after boot system shutdown. This
|
||
is useful for hands-off automated testing.
|
||
|
||
rcutorture.stall_cpu= [KNL]
|
||
Duration of CPU stall (s) to test RCU CPU stall
|
||
warnings, zero to disable.
|
||
|
||
rcutorture.stall_cpu_block= [KNL]
|
||
Sleep while stalling if set. This will result
|
||
in warnings from preemptible RCU in addition to
|
||
any other stall-related activity. Note that
|
||
in kernels built with CONFIG_PREEMPTION=n and
|
||
CONFIG_PREEMPT_COUNT=y, this parameter will
|
||
cause the CPU to pass through a quiescent state.
|
||
Given CONFIG_PREEMPTION=n, this will suppress
|
||
RCU CPU stall warnings, but will instead result
|
||
in scheduling-while-atomic splats.
|
||
|
||
Use of this module parameter results in splats.
|
||
|
||
|
||
rcutorture.stall_cpu_holdoff= [KNL]
|
||
Time to wait (s) after boot before inducing stall.
|
||
|
||
rcutorture.stall_cpu_irqsoff= [KNL]
|
||
Disable interrupts while stalling if set, but only
|
||
on the first stall in the set.
|
||
|
||
rcutorture.stall_cpu_repeat= [KNL]
|
||
Number of times to repeat the stall sequence,
|
||
so that rcutorture.stall_cpu_repeat=3 will result
|
||
in four stall sequences.
|
||
|
||
rcutorture.stall_gp_kthread= [KNL]
|
||
Duration (s) of forced sleep within RCU
|
||
grace-period kthread to test RCU CPU stall
|
||
warnings, zero to disable. If both stall_cpu
|
||
and stall_gp_kthread are specified, the
|
||
kthread is starved first, then the CPU.
|
||
|
||
rcutorture.stat_interval= [KNL]
|
||
Time (s) between statistics printk()s.
|
||
|
||
rcutorture.stutter= [KNL]
|
||
Time (s) to stutter testing, for example, specifying
|
||
five seconds causes the test to run for five seconds,
|
||
wait for five seconds, and so on. This tests RCU's
|
||
ability to transition abruptly to and from idle.
|
||
|
||
rcutorture.test_boost= [KNL]
|
||
Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
|
||
"Maybe" means test if the RCU implementation
|
||
under test support RCU priority boosting.
|
||
|
||
rcutorture.test_boost_duration= [KNL]
|
||
Duration (s) of each individual boost test.
|
||
|
||
rcutorture.test_boost_interval= [KNL]
|
||
Interval (s) between each boost test.
|
||
|
||
rcutorture.test_no_idle_hz= [KNL]
|
||
Test RCU's dyntick-idle handling. See also the
|
||
rcutorture.shuffle_interval parameter.
|
||
|
||
rcutorture.torture_type= [KNL]
|
||
Specify the RCU implementation to test.
|
||
|
||
rcutorture.verbose= [KNL]
|
||
Enable additional printk() statements.
|
||
|
||
rcupdate.rcu_cpu_stall_ftrace_dump= [KNL]
|
||
Dump ftrace buffer after reporting RCU CPU
|
||
stall warning.
|
||
|
||
rcupdate.rcu_cpu_stall_notifiers= [KNL]
|
||
Provide RCU CPU stall notifiers, but see the
|
||
warnings in the RCU_CPU_STALL_NOTIFIER Kconfig
|
||
option's help text. TL;DR: You almost certainly
|
||
do not want rcupdate.rcu_cpu_stall_notifiers.
|
||
|
||
rcupdate.rcu_cpu_stall_suppress= [KNL]
|
||
Suppress RCU CPU stall warning messages.
|
||
|
||
rcupdate.rcu_cpu_stall_suppress_at_boot= [KNL]
|
||
Suppress RCU CPU stall warning messages and
|
||
rcutorture writer stall warnings that occur
|
||
during early boot, that is, during the time
|
||
before the init task is spawned.
|
||
|
||
rcupdate.rcu_cpu_stall_timeout= [KNL]
|
||
Set timeout for RCU CPU stall warning messages.
|
||
The value is in seconds and the maximum allowed
|
||
value is 300 seconds.
|
||
|
||
rcupdate.rcu_exp_cpu_stall_timeout= [KNL]
|
||
Set timeout for expedited RCU CPU stall warning
|
||
messages. The value is in milliseconds
|
||
and the maximum allowed value is 21000
|
||
milliseconds. Please note that this value is
|
||
adjusted to an arch timer tick resolution.
|
||
Setting this to zero causes the value from
|
||
rcupdate.rcu_cpu_stall_timeout to be used (after
|
||
conversion from seconds to milliseconds).
|
||
|
||
rcupdate.rcu_cpu_stall_cputime= [KNL]
|
||
Provide statistics on the cputime and count of
|
||
interrupts and tasks during the sampling period. For
|
||
multiple continuous RCU stalls, all sampling periods
|
||
begin at half of the first RCU stall timeout.
|
||
|
||
rcupdate.rcu_exp_stall_task_details= [KNL]
|
||
Print stack dumps of any tasks blocking the
|
||
current expedited RCU grace period during an
|
||
expedited RCU CPU stall warning.
|
||
|
||
rcupdate.rcu_expedited= [KNL]
|
||
Use expedited grace-period primitives, for
|
||
example, synchronize_rcu_expedited() instead
|
||
of synchronize_rcu(). This reduces latency,
|
||
but can increase CPU utilization, degrade
|
||
real-time latency, and degrade energy efficiency.
|
||
No effect on CONFIG_TINY_RCU kernels.
|
||
|
||
rcupdate.rcu_normal= [KNL]
|
||
Use only normal grace-period primitives,
|
||
for example, synchronize_rcu() instead of
|
||
synchronize_rcu_expedited(). This improves
|
||
real-time latency, CPU utilization, and
|
||
energy efficiency, but can expose users to
|
||
increased grace-period latency. This parameter
|
||
overrides rcupdate.rcu_expedited. No effect on
|
||
CONFIG_TINY_RCU kernels.
|
||
|
||
rcupdate.rcu_normal_after_boot= [KNL]
|
||
Once boot has completed (that is, after
|
||
rcu_end_inkernel_boot() has been invoked), use
|
||
only normal grace-period primitives. No effect
|
||
on CONFIG_TINY_RCU kernels.
|
||
|
||
But note that CONFIG_PREEMPT_RT=y kernels enables
|
||
this kernel boot parameter, forcibly setting
|
||
it to the value one, that is, converting any
|
||
post-boot attempt at an expedited RCU grace
|
||
period to instead use normal non-expedited
|
||
grace-period processing.
|
||
|
||
rcupdate.rcu_task_collapse_lim= [KNL]
|
||
Set the maximum number of callbacks present
|
||
at the beginning of a grace period that allows
|
||
the RCU Tasks flavors to collapse back to using
|
||
a single callback queue. This switching only
|
||
occurs when rcupdate.rcu_task_enqueue_lim is
|
||
set to the default value of -1.
|
||
|
||
rcupdate.rcu_task_contend_lim= [KNL]
|
||
Set the minimum number of callback-queuing-time
|
||
lock-contention events per jiffy required to
|
||
cause the RCU Tasks flavors to switch to per-CPU
|
||
callback queuing. This switching only occurs
|
||
when rcupdate.rcu_task_enqueue_lim is set to
|
||
the default value of -1.
|
||
|
||
rcupdate.rcu_task_enqueue_lim= [KNL]
|
||
Set the number of callback queues to use for the
|
||
RCU Tasks family of RCU flavors. The default
|
||
of -1 allows this to be automatically (and
|
||
dynamically) adjusted. This parameter is intended
|
||
for use in testing.
|
||
|
||
rcupdate.rcu_task_ipi_delay= [KNL]
|
||
Set time in jiffies during which RCU tasks will
|
||
avoid sending IPIs, starting with the beginning
|
||
of a given grace period. Setting a large
|
||
number avoids disturbing real-time workloads,
|
||
but lengthens grace periods.
|
||
|
||
rcupdate.rcu_task_lazy_lim= [KNL]
|
||
Number of callbacks on a given CPU that will
|
||
cancel laziness on that CPU. Use -1 to disable
|
||
cancellation of laziness, but be advised that
|
||
doing so increases the danger of OOM due to
|
||
callback flooding.
|
||
|
||
rcupdate.rcu_task_stall_info= [KNL]
|
||
Set initial timeout in jiffies for RCU task stall
|
||
informational messages, which give some indication
|
||
of the problem for those not patient enough to
|
||
wait for ten minutes. Informational messages are
|
||
only printed prior to the stall-warning message
|
||
for a given grace period. Disable with a value
|
||
less than or equal to zero. Defaults to ten
|
||
seconds. A change in value does not take effect
|
||
until the beginning of the next grace period.
|
||
|
||
rcupdate.rcu_task_stall_info_mult= [KNL]
|
||
Multiplier for time interval between successive
|
||
RCU task stall informational messages for a given
|
||
RCU tasks grace period. This value is clamped
|
||
to one through ten, inclusive. It defaults to
|
||
the value three, so that the first informational
|
||
message is printed 10 seconds into the grace
|
||
period, the second at 40 seconds, the third at
|
||
160 seconds, and then the stall warning at 600
|
||
seconds would prevent a fourth at 640 seconds.
|
||
|
||
rcupdate.rcu_task_stall_timeout= [KNL]
|
||
Set timeout in jiffies for RCU task stall
|
||
warning messages. Disable with a value less
|
||
than or equal to zero. Defaults to ten minutes.
|
||
A change in value does not take effect until
|
||
the beginning of the next grace period.
|
||
|
||
rcupdate.rcu_tasks_lazy_ms= [KNL]
|
||
Set timeout in milliseconds RCU Tasks asynchronous
|
||
callback batching for call_rcu_tasks().
|
||
A negative value will take the default. A value
|
||
of zero will disable batching. Batching is
|
||
always disabled for synchronize_rcu_tasks().
|
||
|
||
rcupdate.rcu_tasks_trace_lazy_ms= [KNL]
|
||
Set timeout in milliseconds RCU Tasks
|
||
Trace asynchronous callback batching for
|
||
call_rcu_tasks_trace(). A negative value
|
||
will take the default. A value of zero will
|
||
disable batching. Batching is always disabled
|
||
for synchronize_rcu_tasks_trace().
|
||
|
||
rcupdate.rcu_self_test= [KNL]
|
||
Run the RCU early boot self tests
|
||
|
||
rdinit= [KNL]
|
||
Format: <full_path>
|
||
Run specified binary instead of /init from the ramdisk,
|
||
used for early userspace startup. See initrd.
|
||
|
||
rdrand= [X86,EARLY]
|
||
force - Override the decision by the kernel to hide the
|
||
advertisement of RDRAND support (this affects
|
||
certain AMD processors because of buggy BIOS
|
||
support, specifically around the suspend/resume
|
||
path).
|
||
|
||
rdt= [HW,X86,RDT]
|
||
Turn on/off individual RDT features. List is:
|
||
cmt, mbmtotal, mbmlocal, l3cat, l3cdp, l2cat, l2cdp,
|
||
mba, smba, bmec.
|
||
E.g. to turn on cmt and turn off mba use:
|
||
rdt=cmt,!mba
|
||
|
||
reboot= [KNL]
|
||
Format (x86 or x86_64):
|
||
[w[arm] | c[old] | h[ard] | s[oft] | g[pio]] | d[efault] \
|
||
[[,]s[mp]#### \
|
||
[[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
|
||
[[,]f[orce]
|
||
Where reboot_mode is one of warm (soft) or cold (hard) or gpio
|
||
(prefix with 'panic_' to set mode for panic
|
||
reboot only),
|
||
reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
|
||
reboot_force is either force or not specified,
|
||
reboot_cpu is s[mp]#### with #### being the processor
|
||
to be used for rebooting.
|
||
|
||
refscale.holdoff= [KNL]
|
||
Set test-start holdoff period. The purpose of
|
||
this parameter is to delay the start of the
|
||
test until boot completes in order to avoid
|
||
interference.
|
||
|
||
refscale.lookup_instances= [KNL]
|
||
Number of data elements to use for the forms of
|
||
SLAB_TYPESAFE_BY_RCU testing. A negative number
|
||
is negated and multiplied by nr_cpu_ids, while
|
||
zero specifies nr_cpu_ids.
|
||
|
||
refscale.loops= [KNL]
|
||
Set the number of loops over the synchronization
|
||
primitive under test. Increasing this number
|
||
reduces noise due to loop start/end overhead,
|
||
but the default has already reduced the per-pass
|
||
noise to a handful of picoseconds on ca. 2020
|
||
x86 laptops.
|
||
|
||
refscale.nreaders= [KNL]
|
||
Set number of readers. The default value of -1
|
||
selects N, where N is roughly 75% of the number
|
||
of CPUs. A value of zero is an interesting choice.
|
||
|
||
refscale.nruns= [KNL]
|
||
Set number of runs, each of which is dumped onto
|
||
the console log.
|
||
|
||
refscale.readdelay= [KNL]
|
||
Set the read-side critical-section duration,
|
||
measured in microseconds.
|
||
|
||
refscale.scale_type= [KNL]
|
||
Specify the read-protection implementation to test.
|
||
|
||
refscale.shutdown= [KNL]
|
||
Shut down the system at the end of the performance
|
||
test. This defaults to 1 (shut it down) when
|
||
refscale is built into the kernel and to 0 (leave
|
||
it running) when refscale is built as a module.
|
||
|
||
refscale.verbose= [KNL]
|
||
Enable additional printk() statements.
|
||
|
||
refscale.verbose_batched= [KNL]
|
||
Batch the additional printk() statements. If zero
|
||
(the default) or negative, print everything. Otherwise,
|
||
print every Nth verbose statement, where N is the value
|
||
specified.
|
||
|
||
regulator_ignore_unused
|
||
[REGULATOR]
|
||
Prevents regulator framework from disabling regulators
|
||
that are unused, due no driver claiming them. This may
|
||
be useful for debug and development, but should not be
|
||
needed on a platform with proper driver support.
|
||
|
||
relax_domain_level=
|
||
[KNL, SMP] Set scheduler's default relax_domain_level.
|
||
See Documentation/admin-guide/cgroup-v1/cpusets.rst.
|
||
|
||
reserve= [KNL,BUGS] Force kernel to ignore I/O ports or memory
|
||
Format: <base1>,<size1>[,<base2>,<size2>,...]
|
||
Reserve I/O ports or memory so the kernel won't use
|
||
them. If <base> is less than 0x10000, the region
|
||
is assumed to be I/O ports; otherwise it is memory.
|
||
|
||
reserve_mem= [RAM]
|
||
Format: nn[KNG]:<align>:<label>
|
||
Reserve physical memory and label it with a name that
|
||
other subsystems can use to access it. This is typically
|
||
used for systems that do not wipe the RAM, and this command
|
||
line will try to reserve the same physical memory on
|
||
soft reboots. Note, it is not guaranteed to be the same
|
||
location. For example, if anything about the system changes
|
||
or if booting a different kernel. It can also fail if KASLR
|
||
places the kernel at the location of where the RAM reservation
|
||
was from a previous boot, the new reservation will be at a
|
||
different location.
|
||
Any subsystem using this feature must add a way to verify
|
||
that the contents of the physical memory is from a previous
|
||
boot, as there may be cases where the memory will not be
|
||
located at the same location.
|
||
|
||
The format is size:align:label for example, to request
|
||
12 megabytes of 4096 alignment for ramoops:
|
||
|
||
reserve_mem=12M:4096:oops ramoops.mem_name=oops
|
||
|
||
reservetop= [X86-32,EARLY]
|
||
Format: nn[KMG]
|
||
Reserves a hole at the top of the kernel virtual
|
||
address space.
|
||
|
||
reset_devices [KNL] Force drivers to reset the underlying device
|
||
during initialization.
|
||
|
||
resume= [SWSUSP]
|
||
Specify the partition device for software suspend
|
||
Format:
|
||
{/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
|
||
|
||
resume_offset= [SWSUSP]
|
||
Specify the offset from the beginning of the partition
|
||
given by "resume=" at which the swap header is located,
|
||
in <PAGE_SIZE> units (needed only for swap files).
|
||
See Documentation/power/swsusp-and-swap-files.rst
|
||
|
||
resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
|
||
read the resume files
|
||
|
||
resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
|
||
Useful for devices that are detected asynchronously
|
||
(e.g. USB and MMC devices).
|
||
|
||
retain_initrd [RAM] Keep initrd memory after extraction. After boot, it will
|
||
be accessible via /sys/firmware/initrd.
|
||
|
||
retbleed= [X86] Control mitigation of RETBleed (Arbitrary
|
||
Speculative Code Execution with Return Instructions)
|
||
vulnerability.
|
||
|
||
AMD-based UNRET and IBPB mitigations alone do not stop
|
||
sibling threads from influencing the predictions of other
|
||
sibling threads. For that reason, STIBP is used on pro-
|
||
cessors that support it, and mitigate SMT on processors
|
||
that don't.
|
||
|
||
off - no mitigation
|
||
auto - automatically select a migitation
|
||
auto,nosmt - automatically select a mitigation,
|
||
disabling SMT if necessary for
|
||
the full mitigation (only on Zen1
|
||
and older without STIBP).
|
||
ibpb - On AMD, mitigate short speculation
|
||
windows on basic block boundaries too.
|
||
Safe, highest perf impact. It also
|
||
enables STIBP if present. Not suitable
|
||
on Intel.
|
||
ibpb,nosmt - Like "ibpb" above but will disable SMT
|
||
when STIBP is not available. This is
|
||
the alternative for systems which do not
|
||
have STIBP.
|
||
unret - Force enable untrained return thunks,
|
||
only effective on AMD f15h-f17h based
|
||
systems.
|
||
unret,nosmt - Like unret, but will disable SMT when STIBP
|
||
is not available. This is the alternative for
|
||
systems which do not have STIBP.
|
||
|
||
Selecting 'auto' will choose a mitigation method at run
|
||
time according to the CPU.
|
||
|
||
Not specifying this option is equivalent to retbleed=auto.
|
||
|
||
rfkill.default_state=
|
||
0 "airplane mode". All wifi, bluetooth, wimax, gps, fm,
|
||
etc. communication is blocked by default.
|
||
1 Unblocked.
|
||
|
||
rfkill.master_switch_mode=
|
||
0 The "airplane mode" button does nothing.
|
||
1 The "airplane mode" button toggles between everything
|
||
blocked and the previous configuration.
|
||
2 The "airplane mode" button toggles between everything
|
||
blocked and everything unblocked.
|
||
|
||
ring3mwait=disable
|
||
[KNL] Disable ring 3 MONITOR/MWAIT feature on supported
|
||
CPUs.
|
||
|
||
riscv_isa_fallback [RISCV,EARLY]
|
||
When CONFIG_RISCV_ISA_FALLBACK is not enabled, permit
|
||
falling back to detecting extension support by parsing
|
||
"riscv,isa" property on devicetree systems when the
|
||
replacement properties are not found. See the Kconfig
|
||
entry for RISCV_ISA_FALLBACK.
|
||
|
||
ro [KNL] Mount root device read-only on boot
|
||
|
||
rodata= [KNL,EARLY]
|
||
on Mark read-only kernel memory as read-only (default).
|
||
off Leave read-only kernel memory writable for debugging.
|
||
full Mark read-only kernel memory and aliases as read-only
|
||
[arm64]
|
||
|
||
rockchip.usb_uart
|
||
[EARLY]
|
||
Enable the uart passthrough on the designated usb port
|
||
on Rockchip SoCs. When active, the signals of the
|
||
debug-uart get routed to the D+ and D- pins of the usb
|
||
port and the regular usb controller gets disabled.
|
||
|
||
root= [KNL] Root filesystem
|
||
Usually this a a block device specifier of some kind,
|
||
see the early_lookup_bdev comment in
|
||
block/early-lookup.c for details.
|
||
Alternatively this can be "ram" for the legacy initial
|
||
ramdisk, "nfs" and "cifs" for root on a network file
|
||
system, or "mtd" and "ubi" for mounting from raw flash.
|
||
|
||
rootdelay= [KNL] Delay (in seconds) to pause before attempting to
|
||
mount the root filesystem
|
||
|
||
rootflags= [KNL] Set root filesystem mount option string
|
||
|
||
rootfstype= [KNL] Set root filesystem type
|
||
|
||
rootwait [KNL] Wait (indefinitely) for root device to show up.
|
||
Useful for devices that are detected asynchronously
|
||
(e.g. USB and MMC devices).
|
||
|
||
rootwait= [KNL] Maximum time (in seconds) to wait for root device
|
||
to show up before attempting to mount the root
|
||
filesystem.
|
||
|
||
rproc_mem=nn[KMG][@address]
|
||
[KNL,ARM,CMA] Remoteproc physical memory block.
|
||
Memory area to be used by remote processor image,
|
||
managed by CMA.
|
||
|
||
rw [KNL] Mount root device read-write on boot
|
||
|
||
S [KNL] Run init in single mode
|
||
|
||
s390_iommu= [HW,S390]
|
||
Set s390 IOTLB flushing mode
|
||
strict
|
||
With strict flushing every unmap operation will result
|
||
in an IOTLB flush. Default is lazy flushing before
|
||
reuse, which is faster. Deprecated, equivalent to
|
||
iommu.strict=1.
|
||
|
||
s390_iommu_aperture= [KNL,S390]
|
||
Specifies the size of the per device DMA address space
|
||
accessible through the DMA and IOMMU APIs as a decimal
|
||
factor of the size of main memory.
|
||
The default is 1 meaning that one can concurrently use
|
||
as many DMA addresses as physical memory is installed,
|
||
if supported by hardware, and thus map all of memory
|
||
once. With a value of 2 one can map all of memory twice
|
||
and so on. As a special case a factor of 0 imposes no
|
||
restrictions other than those given by hardware at the
|
||
cost of significant additional memory use for tables.
|
||
|
||
sa1100ir [NET]
|
||
See drivers/net/irda/sa1100_ir.c.
|
||
|
||
sched_verbose [KNL,EARLY] Enables verbose scheduler debug messages.
|
||
|
||
schedstats= [KNL,X86] Enable or disable scheduled statistics.
|
||
Allowed values are enable and disable. This feature
|
||
incurs a small amount of overhead in the scheduler
|
||
but is useful for debugging and performance tuning.
|
||
|
||
sched_thermal_decay_shift=
|
||
[Deprecated]
|
||
[KNL, SMP] Set a decay shift for scheduler thermal
|
||
pressure signal. Thermal pressure signal follows the
|
||
default decay period of other scheduler pelt
|
||
signals(usually 32 ms but configurable). Setting
|
||
sched_thermal_decay_shift will left shift the decay
|
||
period for the thermal pressure signal by the shift
|
||
value.
|
||
i.e. with the default pelt decay period of 32 ms
|
||
sched_thermal_decay_shift thermal pressure decay pr
|
||
1 64 ms
|
||
2 128 ms
|
||
and so on.
|
||
Format: integer between 0 and 10
|
||
Default is 0.
|
||
|
||
scftorture.holdoff= [KNL]
|
||
Number of seconds to hold off before starting
|
||
test. Defaults to zero for module insertion and
|
||
to 10 seconds for built-in smp_call_function()
|
||
tests.
|
||
|
||
scftorture.longwait= [KNL]
|
||
Request ridiculously long waits randomly selected
|
||
up to the chosen limit in seconds. Zero (the
|
||
default) disables this feature. Please note
|
||
that requesting even small non-zero numbers of
|
||
seconds can result in RCU CPU stall warnings,
|
||
softlockup complaints, and so on.
|
||
|
||
scftorture.nthreads= [KNL]
|
||
Number of kthreads to spawn to invoke the
|
||
smp_call_function() family of functions.
|
||
The default of -1 specifies a number of kthreads
|
||
equal to the number of CPUs.
|
||
|
||
scftorture.onoff_holdoff= [KNL]
|
||
Number seconds to wait after the start of the
|
||
test before initiating CPU-hotplug operations.
|
||
|
||
scftorture.onoff_interval= [KNL]
|
||
Number seconds to wait between successive
|
||
CPU-hotplug operations. Specifying zero (which
|
||
is the default) disables CPU-hotplug operations.
|
||
|
||
scftorture.shutdown_secs= [KNL]
|
||
The number of seconds following the start of the
|
||
test after which to shut down the system. The
|
||
default of zero avoids shutting down the system.
|
||
Non-zero values are useful for automated tests.
|
||
|
||
scftorture.stat_interval= [KNL]
|
||
The number of seconds between outputting the
|
||
current test statistics to the console. A value
|
||
of zero disables statistics output.
|
||
|
||
scftorture.stutter_cpus= [KNL]
|
||
The number of jiffies to wait between each change
|
||
to the set of CPUs under test.
|
||
|
||
scftorture.use_cpus_read_lock= [KNL]
|
||
Use use_cpus_read_lock() instead of the default
|
||
preempt_disable() to disable CPU hotplug
|
||
while invoking one of the smp_call_function*()
|
||
functions.
|
||
|
||
scftorture.verbose= [KNL]
|
||
Enable additional printk() statements.
|
||
|
||
scftorture.weight_single= [KNL]
|
||
The probability weighting to use for the
|
||
smp_call_function_single() function with a zero
|
||
"wait" parameter. A value of -1 selects the
|
||
default if all other weights are -1. However,
|
||
if at least one weight has some other value, a
|
||
value of -1 will instead select a weight of zero.
|
||
|
||
scftorture.weight_single_wait= [KNL]
|
||
The probability weighting to use for the
|
||
smp_call_function_single() function with a
|
||
non-zero "wait" parameter. See weight_single.
|
||
|
||
scftorture.weight_many= [KNL]
|
||
The probability weighting to use for the
|
||
smp_call_function_many() function with a zero
|
||
"wait" parameter. See weight_single.
|
||
Note well that setting a high probability for
|
||
this weighting can place serious IPI load
|
||
on the system.
|
||
|
||
scftorture.weight_many_wait= [KNL]
|
||
The probability weighting to use for the
|
||
smp_call_function_many() function with a
|
||
non-zero "wait" parameter. See weight_single
|
||
and weight_many.
|
||
|
||
scftorture.weight_all= [KNL]
|
||
The probability weighting to use for the
|
||
smp_call_function_all() function with a zero
|
||
"wait" parameter. See weight_single and
|
||
weight_many.
|
||
|
||
scftorture.weight_all_wait= [KNL]
|
||
The probability weighting to use for the
|
||
smp_call_function_all() function with a
|
||
non-zero "wait" parameter. See weight_single
|
||
and weight_many.
|
||
|
||
skew_tick= [KNL,EARLY] Offset the periodic timer tick per cpu to mitigate
|
||
xtime_lock contention on larger systems, and/or RCU lock
|
||
contention on all systems with CONFIG_MAXSMP set.
|
||
Format: { "0" | "1" }
|
||
0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
|
||
1 -- enable.
|
||
Note: increases power consumption, thus should only be
|
||
enabled if running jitter sensitive (HPC/RT) workloads.
|
||
|
||
security= [SECURITY] Choose a legacy "major" security module to
|
||
enable at boot. This has been deprecated by the
|
||
"lsm=" parameter.
|
||
|
||
selinux= [SELINUX] Disable or enable SELinux at boot time.
|
||
Format: { "0" | "1" }
|
||
See security/selinux/Kconfig help text.
|
||
0 -- disable.
|
||
1 -- enable.
|
||
Default value is 1.
|
||
|
||
serialnumber [BUGS=X86-32]
|
||
|
||
sev=option[,option...] [X86-64] See Documentation/arch/x86/x86_64/boot-options.rst
|
||
|
||
shapers= [NET]
|
||
Maximal number of shapers.
|
||
|
||
show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
|
||
Limit apic dumping. The parameter defines the maximal
|
||
number of local apics being dumped. Also it is possible
|
||
to set it to "all" by meaning -- no limit here.
|
||
Format: { 1 (default) | 2 | ... | all }.
|
||
The parameter valid if only apic=debug or
|
||
apic=verbose is specified.
|
||
Example: apic=debug show_lapic=all
|
||
|
||
slab_debug[=options[,slabs][;[options[,slabs]]...] [MM]
|
||
Enabling slab_debug allows one to determine the
|
||
culprit if slab objects become corrupted. Enabling
|
||
slab_debug can create guard zones around objects and
|
||
may poison objects when not in use. Also tracks the
|
||
last alloc / free. For more information see
|
||
Documentation/mm/slub.rst.
|
||
(slub_debug legacy name also accepted for now)
|
||
|
||
slab_max_order= [MM]
|
||
Determines the maximum allowed order for slabs.
|
||
A high setting may cause OOMs due to memory
|
||
fragmentation. For more information see
|
||
Documentation/mm/slub.rst.
|
||
(slub_max_order legacy name also accepted for now)
|
||
|
||
slab_merge [MM]
|
||
Enable merging of slabs with similar size when the
|
||
kernel is built without CONFIG_SLAB_MERGE_DEFAULT.
|
||
(slub_merge legacy name also accepted for now)
|
||
|
||
slab_min_objects= [MM]
|
||
The minimum number of objects per slab. SLUB will
|
||
increase the slab order up to slab_max_order to
|
||
generate a sufficiently large slab able to contain
|
||
the number of objects indicated. The higher the number
|
||
of objects the smaller the overhead of tracking slabs
|
||
and the less frequently locks need to be acquired.
|
||
For more information see Documentation/mm/slub.rst.
|
||
(slub_min_objects legacy name also accepted for now)
|
||
|
||
slab_min_order= [MM]
|
||
Determines the minimum page order for slabs. Must be
|
||
lower or equal to slab_max_order. For more information see
|
||
Documentation/mm/slub.rst.
|
||
(slub_min_order legacy name also accepted for now)
|
||
|
||
slab_nomerge [MM]
|
||
Disable merging of slabs with similar size. May be
|
||
necessary if there is some reason to distinguish
|
||
allocs to different slabs, especially in hardened
|
||
environments where the risk of heap overflows and
|
||
layout control by attackers can usually be
|
||
frustrated by disabling merging. This will reduce
|
||
most of the exposure of a heap attack to a single
|
||
cache (risks via metadata attacks are mostly
|
||
unchanged). Debug options disable merging on their
|
||
own.
|
||
For more information see Documentation/mm/slub.rst.
|
||
(slub_nomerge legacy name also accepted for now)
|
||
|
||
slram= [HW,MTD]
|
||
|
||
smart2= [HW]
|
||
Format: <io1>[,<io2>[,...,<io8>]]
|
||
|
||
smp.csd_lock_timeout= [KNL]
|
||
Specify the period of time in milliseconds
|
||
that smp_call_function() and friends will wait
|
||
for a CPU to release the CSD lock. This is
|
||
useful when diagnosing bugs involving CPUs
|
||
disabling interrupts for extended periods
|
||
of time. Defaults to 5,000 milliseconds, and
|
||
setting a value of zero disables this feature.
|
||
This feature may be more efficiently disabled
|
||
using the csdlock_debug- kernel parameter.
|
||
|
||
smp.panic_on_ipistall= [KNL]
|
||
If a csd_lock_timeout extends for more than
|
||
the specified number of milliseconds, panic the
|
||
system. By default, let CSD-lock acquisition
|
||
take as long as they take. Specifying 300,000
|
||
for this value provides a 5-minute timeout.
|
||
|
||
smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
|
||
smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
|
||
smsc-ircc2.ircc_sir= [HW] SIR base I/O port
|
||
smsc-ircc2.ircc_fir= [HW] FIR base I/O port
|
||
smsc-ircc2.ircc_irq= [HW] IRQ line
|
||
smsc-ircc2.ircc_dma= [HW] DMA channel
|
||
smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
|
||
0: Toshiba Satellite 1800 (GP data pin select)
|
||
1: Fast pin select (default)
|
||
2: ATC IRMode
|
||
|
||
smt= [KNL,MIPS,S390,EARLY] Set the maximum number of threads
|
||
(logical CPUs) to use per physical CPU on systems
|
||
capable of symmetric multithreading (SMT). Will
|
||
be capped to the actual hardware limit.
|
||
Format: <integer>
|
||
Default: -1 (no limit)
|
||
|
||
softlockup_panic=
|
||
[KNL] Should the soft-lockup detector generate panics.
|
||
Format: 0 | 1
|
||
|
||
A value of 1 instructs the soft-lockup detector
|
||
to panic the machine when a soft-lockup occurs. It is
|
||
also controlled by the kernel.softlockup_panic sysctl
|
||
and CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC, which is the
|
||
respective build-time switch to that functionality.
|
||
|
||
softlockup_all_cpu_backtrace=
|
||
[KNL] Should the soft-lockup detector generate
|
||
backtraces on all cpus.
|
||
Format: 0 | 1
|
||
|
||
sonypi.*= [HW] Sony Programmable I/O Control Device driver
|
||
See Documentation/admin-guide/laptops/sonypi.rst
|
||
|
||
spectre_bhi= [X86] Control mitigation of Branch History Injection
|
||
(BHI) vulnerability. This setting affects the
|
||
deployment of the HW BHI control and the SW BHB
|
||
clearing sequence.
|
||
|
||
on - (default) Enable the HW or SW mitigation as
|
||
needed. This protects the kernel from
|
||
both syscalls and VMs.
|
||
vmexit - On systems which don't have the HW mitigation
|
||
available, enable the SW mitigation on vmexit
|
||
ONLY. On such systems, the host kernel is
|
||
protected from VM-originated BHI attacks, but
|
||
may still be vulnerable to syscall attacks.
|
||
off - Disable the mitigation.
|
||
|
||
spectre_v2= [X86,EARLY] Control mitigation of Spectre variant 2
|
||
(indirect branch speculation) vulnerability.
|
||
The default operation protects the kernel from
|
||
user space attacks.
|
||
|
||
on - unconditionally enable, implies
|
||
spectre_v2_user=on
|
||
off - unconditionally disable, implies
|
||
spectre_v2_user=off
|
||
auto - kernel detects whether your CPU model is
|
||
vulnerable
|
||
|
||
Selecting 'on' will, and 'auto' may, choose a
|
||
mitigation method at run time according to the
|
||
CPU, the available microcode, the setting of the
|
||
CONFIG_MITIGATION_RETPOLINE configuration option,
|
||
and the compiler with which the kernel was built.
|
||
|
||
Selecting 'on' will also enable the mitigation
|
||
against user space to user space task attacks.
|
||
|
||
Selecting 'off' will disable both the kernel and
|
||
the user space protections.
|
||
|
||
Specific mitigations can also be selected manually:
|
||
|
||
retpoline - replace indirect branches
|
||
retpoline,generic - Retpolines
|
||
retpoline,lfence - LFENCE; indirect branch
|
||
retpoline,amd - alias for retpoline,lfence
|
||
eibrs - Enhanced/Auto IBRS
|
||
eibrs,retpoline - Enhanced/Auto IBRS + Retpolines
|
||
eibrs,lfence - Enhanced/Auto IBRS + LFENCE
|
||
ibrs - use IBRS to protect kernel
|
||
|
||
Not specifying this option is equivalent to
|
||
spectre_v2=auto.
|
||
|
||
spectre_v2_user=
|
||
[X86] Control mitigation of Spectre variant 2
|
||
(indirect branch speculation) vulnerability between
|
||
user space tasks
|
||
|
||
on - Unconditionally enable mitigations. Is
|
||
enforced by spectre_v2=on
|
||
|
||
off - Unconditionally disable mitigations. Is
|
||
enforced by spectre_v2=off
|
||
|
||
prctl - Indirect branch speculation is enabled,
|
||
but mitigation can be enabled via prctl
|
||
per thread. The mitigation control state
|
||
is inherited on fork.
|
||
|
||
prctl,ibpb
|
||
- Like "prctl" above, but only STIBP is
|
||
controlled per thread. IBPB is issued
|
||
always when switching between different user
|
||
space processes.
|
||
|
||
seccomp
|
||
- Same as "prctl" above, but all seccomp
|
||
threads will enable the mitigation unless
|
||
they explicitly opt out.
|
||
|
||
seccomp,ibpb
|
||
- Like "seccomp" above, but only STIBP is
|
||
controlled per thread. IBPB is issued
|
||
always when switching between different
|
||
user space processes.
|
||
|
||
auto - Kernel selects the mitigation depending on
|
||
the available CPU features and vulnerability.
|
||
|
||
Default mitigation: "prctl"
|
||
|
||
Not specifying this option is equivalent to
|
||
spectre_v2_user=auto.
|
||
|
||
spec_rstack_overflow=
|
||
[X86,EARLY] Control RAS overflow mitigation on AMD Zen CPUs
|
||
|
||
off - Disable mitigation
|
||
microcode - Enable microcode mitigation only
|
||
safe-ret - Enable sw-only safe RET mitigation (default)
|
||
ibpb - Enable mitigation by issuing IBPB on
|
||
kernel entry
|
||
ibpb-vmexit - Issue IBPB only on VMEXIT
|
||
(cloud-specific mitigation)
|
||
|
||
spec_store_bypass_disable=
|
||
[HW,EARLY] Control Speculative Store Bypass (SSB) Disable mitigation
|
||
(Speculative Store Bypass vulnerability)
|
||
|
||
Certain CPUs are vulnerable to an exploit against a
|
||
a common industry wide performance optimization known
|
||
as "Speculative Store Bypass" in which recent stores
|
||
to the same memory location may not be observed by
|
||
later loads during speculative execution. The idea
|
||
is that such stores are unlikely and that they can
|
||
be detected prior to instruction retirement at the
|
||
end of a particular speculation execution window.
|
||
|
||
In vulnerable processors, the speculatively forwarded
|
||
store can be used in a cache side channel attack, for
|
||
example to read memory to which the attacker does not
|
||
directly have access (e.g. inside sandboxed code).
|
||
|
||
This parameter controls whether the Speculative Store
|
||
Bypass optimization is used.
|
||
|
||
On x86 the options are:
|
||
|
||
on - Unconditionally disable Speculative Store Bypass
|
||
off - Unconditionally enable Speculative Store Bypass
|
||
auto - Kernel detects whether the CPU model contains an
|
||
implementation of Speculative Store Bypass and
|
||
picks the most appropriate mitigation. If the
|
||
CPU is not vulnerable, "off" is selected. If the
|
||
CPU is vulnerable the default mitigation is
|
||
architecture and Kconfig dependent. See below.
|
||
prctl - Control Speculative Store Bypass per thread
|
||
via prctl. Speculative Store Bypass is enabled
|
||
for a process by default. The state of the control
|
||
is inherited on fork.
|
||
seccomp - Same as "prctl" above, but all seccomp threads
|
||
will disable SSB unless they explicitly opt out.
|
||
|
||
Default mitigations:
|
||
X86: "prctl"
|
||
|
||
On powerpc the options are:
|
||
|
||
on,auto - On Power8 and Power9 insert a store-forwarding
|
||
barrier on kernel entry and exit. On Power7
|
||
perform a software flush on kernel entry and
|
||
exit.
|
||
off - No action.
|
||
|
||
Not specifying this option is equivalent to
|
||
spec_store_bypass_disable=auto.
|
||
|
||
split_lock_detect=
|
||
[X86] Enable split lock detection or bus lock detection
|
||
|
||
When enabled (and if hardware support is present), atomic
|
||
instructions that access data across cache line
|
||
boundaries will result in an alignment check exception
|
||
for split lock detection or a debug exception for
|
||
bus lock detection.
|
||
|
||
off - not enabled
|
||
|
||
warn - the kernel will emit rate-limited warnings
|
||
about applications triggering the #AC
|
||
exception or the #DB exception. This mode is
|
||
the default on CPUs that support split lock
|
||
detection or bus lock detection. Default
|
||
behavior is by #AC if both features are
|
||
enabled in hardware.
|
||
|
||
fatal - the kernel will send SIGBUS to applications
|
||
that trigger the #AC exception or the #DB
|
||
exception. Default behavior is by #AC if
|
||
both features are enabled in hardware.
|
||
|
||
ratelimit:N -
|
||
Set system wide rate limit to N bus locks
|
||
per second for bus lock detection.
|
||
0 < N <= 1000.
|
||
|
||
N/A for split lock detection.
|
||
|
||
|
||
If an #AC exception is hit in the kernel or in
|
||
firmware (i.e. not while executing in user mode)
|
||
the kernel will oops in either "warn" or "fatal"
|
||
mode.
|
||
|
||
#DB exception for bus lock is triggered only when
|
||
CPL > 0.
|
||
|
||
srbds= [X86,INTEL,EARLY]
|
||
Control the Special Register Buffer Data Sampling
|
||
(SRBDS) mitigation.
|
||
|
||
Certain CPUs are vulnerable to an MDS-like
|
||
exploit which can leak bits from the random
|
||
number generator.
|
||
|
||
By default, this issue is mitigated by
|
||
microcode. However, the microcode fix can cause
|
||
the RDRAND and RDSEED instructions to become
|
||
much slower. Among other effects, this will
|
||
result in reduced throughput from /dev/urandom.
|
||
|
||
The microcode mitigation can be disabled with
|
||
the following option:
|
||
|
||
off: Disable mitigation and remove
|
||
performance impact to RDRAND and RDSEED
|
||
|
||
srcutree.big_cpu_lim [KNL]
|
||
Specifies the number of CPUs constituting a
|
||
large system, such that srcu_struct structures
|
||
should immediately allocate an srcu_node array.
|
||
This kernel-boot parameter defaults to 128,
|
||
but takes effect only when the low-order four
|
||
bits of srcutree.convert_to_big is equal to 3
|
||
(decide at boot).
|
||
|
||
srcutree.convert_to_big [KNL]
|
||
Specifies under what conditions an SRCU tree
|
||
srcu_struct structure will be converted to big
|
||
form, that is, with an rcu_node tree:
|
||
|
||
0: Never.
|
||
1: At init_srcu_struct() time.
|
||
2: When rcutorture decides to.
|
||
3: Decide at boot time (default).
|
||
0x1X: Above plus if high contention.
|
||
|
||
Either way, the srcu_node tree will be sized based
|
||
on the actual runtime number of CPUs (nr_cpu_ids)
|
||
instead of the compile-time CONFIG_NR_CPUS.
|
||
|
||
srcutree.counter_wrap_check [KNL]
|
||
Specifies how frequently to check for
|
||
grace-period sequence counter wrap for the
|
||
srcu_data structure's ->srcu_gp_seq_needed field.
|
||
The greater the number of bits set in this kernel
|
||
parameter, the less frequently counter wrap will
|
||
be checked for. Note that the bottom two bits
|
||
are ignored.
|
||
|
||
srcutree.exp_holdoff [KNL]
|
||
Specifies how many nanoseconds must elapse
|
||
since the end of the last SRCU grace period for
|
||
a given srcu_struct until the next normal SRCU
|
||
grace period will be considered for automatic
|
||
expediting. Set to zero to disable automatic
|
||
expediting.
|
||
|
||
srcutree.srcu_max_nodelay [KNL]
|
||
Specifies the number of no-delay instances
|
||
per jiffy for which the SRCU grace period
|
||
worker thread will be rescheduled with zero
|
||
delay. Beyond this limit, worker thread will
|
||
be rescheduled with a sleep delay of one jiffy.
|
||
|
||
srcutree.srcu_max_nodelay_phase [KNL]
|
||
Specifies the per-grace-period phase, number of
|
||
non-sleeping polls of readers. Beyond this limit,
|
||
grace period worker thread will be rescheduled
|
||
with a sleep delay of one jiffy, between each
|
||
rescan of the readers, for a grace period phase.
|
||
|
||
srcutree.srcu_retry_check_delay [KNL]
|
||
Specifies number of microseconds of non-sleeping
|
||
delay between each non-sleeping poll of readers.
|
||
|
||
srcutree.small_contention_lim [KNL]
|
||
Specifies the number of update-side contention
|
||
events per jiffy will be tolerated before
|
||
initiating a conversion of an srcu_struct
|
||
structure to big form. Note that the value of
|
||
srcutree.convert_to_big must have the 0x10 bit
|
||
set for contention-based conversions to occur.
|
||
|
||
ssbd= [ARM64,HW,EARLY]
|
||
Speculative Store Bypass Disable control
|
||
|
||
On CPUs that are vulnerable to the Speculative
|
||
Store Bypass vulnerability and offer a
|
||
firmware based mitigation, this parameter
|
||
indicates how the mitigation should be used:
|
||
|
||
force-on: Unconditionally enable mitigation for
|
||
for both kernel and userspace
|
||
force-off: Unconditionally disable mitigation for
|
||
for both kernel and userspace
|
||
kernel: Always enable mitigation in the
|
||
kernel, and offer a prctl interface
|
||
to allow userspace to register its
|
||
interest in being mitigated too.
|
||
|
||
stack_guard_gap= [MM]
|
||
override the default stack gap protection. The value
|
||
is in page units and it defines how many pages prior
|
||
to (for stacks growing down) resp. after (for stacks
|
||
growing up) the main stack are reserved for no other
|
||
mapping. Default value is 256 pages.
|
||
|
||
stack_depot_disable= [KNL,EARLY]
|
||
Setting this to true through kernel command line will
|
||
disable the stack depot thereby saving the static memory
|
||
consumed by the stack hash table. By default this is set
|
||
to false.
|
||
|
||
stacktrace [FTRACE]
|
||
Enabled the stack tracer on boot up.
|
||
|
||
stacktrace_filter=[function-list]
|
||
[FTRACE] Limit the functions that the stack tracer
|
||
will trace at boot up. function-list is a comma-separated
|
||
list of functions. This list can be changed at run
|
||
time by the stack_trace_filter file in the debugfs
|
||
tracing directory. Note, this enables stack tracing
|
||
and the stacktrace above is not needed.
|
||
|
||
sti= [PARISC,HW]
|
||
Format: <num>
|
||
Set the STI (builtin display/keyboard on the HP-PARISC
|
||
machines) console (graphic card) which should be used
|
||
as the initial boot-console.
|
||
See also comment in drivers/video/console/sticore.c.
|
||
|
||
sti_font= [HW]
|
||
See comment in drivers/video/console/sticore.c.
|
||
|
||
stifb= [HW]
|
||
Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
|
||
|
||
strict_sas_size=
|
||
[X86]
|
||
Format: <bool>
|
||
Enable or disable strict sigaltstack size checks
|
||
against the required signal frame size which
|
||
depends on the supported FPU features. This can
|
||
be used to filter out binaries which have
|
||
not yet been made aware of AT_MINSIGSTKSZ.
|
||
|
||
stress_hpt [PPC,EARLY]
|
||
Limits the number of kernel HPT entries in the hash
|
||
page table to increase the rate of hash page table
|
||
faults on kernel addresses.
|
||
|
||
stress_slb [PPC,EARLY]
|
||
Limits the number of kernel SLB entries, and flushes
|
||
them frequently to increase the rate of SLB faults
|
||
on kernel addresses.
|
||
|
||
sunrpc.min_resvport=
|
||
sunrpc.max_resvport=
|
||
[NFS,SUNRPC]
|
||
SunRPC servers often require that client requests
|
||
originate from a privileged port (i.e. a port in the
|
||
range 0 < portnr < 1024).
|
||
An administrator who wishes to reserve some of these
|
||
ports for other uses may adjust the range that the
|
||
kernel's sunrpc client considers to be privileged
|
||
using these two parameters to set the minimum and
|
||
maximum port values.
|
||
|
||
sunrpc.svc_rpc_per_connection_limit=
|
||
[NFS,SUNRPC]
|
||
Limit the number of requests that the server will
|
||
process in parallel from a single connection.
|
||
The default value is 0 (no limit).
|
||
|
||
sunrpc.pool_mode=
|
||
[NFS]
|
||
Control how the NFS server code allocates CPUs to
|
||
service thread pools. Depending on how many NICs
|
||
you have and where their interrupts are bound, this
|
||
option will affect which CPUs will do NFS serving.
|
||
Note: this parameter cannot be changed while the
|
||
NFS server is running.
|
||
|
||
auto the server chooses an appropriate mode
|
||
automatically using heuristics
|
||
global a single global pool contains all CPUs
|
||
percpu one pool for each CPU
|
||
pernode one pool for each NUMA node (equivalent
|
||
to global on non-NUMA machines)
|
||
|
||
sunrpc.tcp_slot_table_entries=
|
||
sunrpc.udp_slot_table_entries=
|
||
[NFS,SUNRPC]
|
||
Sets the upper limit on the number of simultaneous
|
||
RPC calls that can be sent from the client to a
|
||
server. Increasing these values may allow you to
|
||
improve throughput, but will also increase the
|
||
amount of memory reserved for use by the client.
|
||
|
||
suspend.pm_test_delay=
|
||
[SUSPEND]
|
||
Sets the number of seconds to remain in a suspend test
|
||
mode before resuming the system (see
|
||
/sys/power/pm_test). Only available when CONFIG_PM_DEBUG
|
||
is set. Default value is 5.
|
||
|
||
svm= [PPC]
|
||
Format: { on | off | y | n | 1 | 0 }
|
||
This parameter controls use of the Protected
|
||
Execution Facility on pSeries.
|
||
|
||
swiotlb= [ARM,PPC,MIPS,X86,S390,EARLY]
|
||
Format: { <int> [,<int>] | force | noforce }
|
||
<int> -- Number of I/O TLB slabs
|
||
<int> -- Second integer after comma. Number of swiotlb
|
||
areas with their own lock. Will be rounded up
|
||
to a power of 2.
|
||
force -- force using of bounce buffers even if they
|
||
wouldn't be automatically used by the kernel
|
||
noforce -- Never use bounce buffers (for debugging)
|
||
|
||
switches= [HW,M68k,EARLY]
|
||
|
||
sysctl.*= [KNL]
|
||
Set a sysctl parameter, right before loading the init
|
||
process, as if the value was written to the respective
|
||
/proc/sys/... file. Both '.' and '/' are recognized as
|
||
separators. Unrecognized parameters and invalid values
|
||
are reported in the kernel log. Sysctls registered
|
||
later by a loaded module cannot be set this way.
|
||
Example: sysctl.vm.swappiness=40
|
||
|
||
sysrq_always_enabled
|
||
[KNL]
|
||
Ignore sysrq setting - this boot parameter will
|
||
neutralize any effect of /proc/sys/kernel/sysrq.
|
||
Useful for debugging.
|
||
|
||
tcpmhash_entries= [KNL,NET]
|
||
Set the number of tcp_metrics_hash slots.
|
||
Default value is 8192 or 16384 depending on total
|
||
ram pages. This is used to specify the TCP metrics
|
||
cache size. See Documentation/networking/ip-sysctl.rst
|
||
"tcp_no_metrics_save" section for more details.
|
||
|
||
tdfx= [HW,DRM]
|
||
|
||
test_suspend= [SUSPEND]
|
||
Format: { "mem" | "standby" | "freeze" }[,N]
|
||
Specify "mem" (for Suspend-to-RAM) or "standby" (for
|
||
standby suspend) or "freeze" (for suspend type freeze)
|
||
as the system sleep state during system startup with
|
||
the optional capability to repeat N number of times.
|
||
The system is woken from this state using a
|
||
wakeup-capable RTC alarm.
|
||
|
||
thash_entries= [KNL,NET]
|
||
Set number of hash buckets for TCP connection
|
||
|
||
thermal.act= [HW,ACPI]
|
||
-1: disable all active trip points in all thermal zones
|
||
<degrees C>: override all lowest active trip points
|
||
|
||
thermal.crt= [HW,ACPI]
|
||
-1: disable all critical trip points in all thermal zones
|
||
<degrees C>: override all critical trip points
|
||
|
||
thermal.off= [HW,ACPI]
|
||
1: disable ACPI thermal control
|
||
|
||
thermal.psv= [HW,ACPI]
|
||
-1: disable all passive trip points
|
||
<degrees C>: override all passive trip points to this
|
||
value
|
||
|
||
thermal.tzp= [HW,ACPI]
|
||
Specify global default ACPI thermal zone polling rate
|
||
<deci-seconds>: poll all this frequency
|
||
0: no polling (default)
|
||
|
||
thp_anon= [KNL]
|
||
Format: <size>,<size>[KMG]:<state>;<size>-<size>[KMG]:<state>
|
||
state is one of "always", "madvise", "never" or "inherit".
|
||
Control the default behavior of the system with respect
|
||
to anonymous transparent hugepages.
|
||
Can be used multiple times for multiple anon THP sizes.
|
||
See Documentation/admin-guide/mm/transhuge.rst for more
|
||
details.
|
||
|
||
threadirqs [KNL,EARLY]
|
||
Force threading of all interrupt handlers except those
|
||
marked explicitly IRQF_NO_THREAD.
|
||
|
||
topology= [S390,EARLY]
|
||
Format: {off | on}
|
||
Specify if the kernel should make use of the cpu
|
||
topology information if the hardware supports this.
|
||
The scheduler will make use of this information and
|
||
e.g. base its process migration decisions on it.
|
||
Default is on.
|
||
|
||
torture.disable_onoff_at_boot= [KNL]
|
||
Prevent the CPU-hotplug component of torturing
|
||
until after init has spawned.
|
||
|
||
torture.ftrace_dump_at_shutdown= [KNL]
|
||
Dump the ftrace buffer at torture-test shutdown,
|
||
even if there were no errors. This can be a
|
||
very costly operation when many torture tests
|
||
are running concurrently, especially on systems
|
||
with rotating-rust storage.
|
||
|
||
torture.verbose_sleep_frequency= [KNL]
|
||
Specifies how many verbose printk()s should be
|
||
emitted between each sleep. The default of zero
|
||
disables verbose-printk() sleeping.
|
||
|
||
torture.verbose_sleep_duration= [KNL]
|
||
Duration of each verbose-printk() sleep in jiffies.
|
||
|
||
tpm_suspend_pcr=[HW,TPM]
|
||
Format: integer pcr id
|
||
Specify that at suspend time, the tpm driver
|
||
should extend the specified pcr with zeros,
|
||
as a workaround for some chips which fail to
|
||
flush the last written pcr on TPM_SaveState.
|
||
This will guarantee that all the other pcrs
|
||
are saved.
|
||
|
||
tpm_tis.interrupts= [HW,TPM]
|
||
Enable interrupts for the MMIO based physical layer
|
||
for the FIFO interface. By default it is set to false
|
||
(0). For more information about TPM hardware interfaces
|
||
defined by Trusted Computing Group (TCG) see
|
||
https://trustedcomputinggroup.org/resource/pc-client-platform-tpm-profile-ptp-specification/
|
||
|
||
tp_printk [FTRACE]
|
||
Have the tracepoints sent to printk as well as the
|
||
tracing ring buffer. This is useful for early boot up
|
||
where the system hangs or reboots and does not give the
|
||
option for reading the tracing buffer or performing a
|
||
ftrace_dump_on_oops.
|
||
|
||
To turn off having tracepoints sent to printk,
|
||
echo 0 > /proc/sys/kernel/tracepoint_printk
|
||
Note, echoing 1 into this file without the
|
||
tp_printk kernel cmdline option has no effect.
|
||
|
||
The tp_printk_stop_on_boot (see below) can also be used
|
||
to stop the printing of events to console at
|
||
late_initcall_sync.
|
||
|
||
** CAUTION **
|
||
|
||
Having tracepoints sent to printk() and activating high
|
||
frequency tracepoints such as irq or sched, can cause
|
||
the system to live lock.
|
||
|
||
tp_printk_stop_on_boot [FTRACE]
|
||
When tp_printk (above) is set, it can cause a lot of noise
|
||
on the console. It may be useful to only include the
|
||
printing of events during boot up, as user space may
|
||
make the system inoperable.
|
||
|
||
This command line option will stop the printing of events
|
||
to console at the late_initcall_sync() time frame.
|
||
|
||
trace_buf_size=nn[KMG]
|
||
[FTRACE] will set tracing buffer size on each cpu.
|
||
|
||
trace_clock= [FTRACE] Set the clock used for tracing events
|
||
at boot up.
|
||
local - Use the per CPU time stamp counter
|
||
(converted into nanoseconds). Fast, but
|
||
depending on the architecture, may not be
|
||
in sync between CPUs.
|
||
global - Event time stamps are synchronize across
|
||
CPUs. May be slower than the local clock,
|
||
but better for some race conditions.
|
||
counter - Simple counting of events (1, 2, ..)
|
||
note, some counts may be skipped due to the
|
||
infrastructure grabbing the clock more than
|
||
once per event.
|
||
uptime - Use jiffies as the time stamp.
|
||
perf - Use the same clock that perf uses.
|
||
mono - Use ktime_get_mono_fast_ns() for time stamps.
|
||
mono_raw - Use ktime_get_raw_fast_ns() for time
|
||
stamps.
|
||
boot - Use ktime_get_boot_fast_ns() for time stamps.
|
||
Architectures may add more clocks. See
|
||
Documentation/trace/ftrace.rst for more details.
|
||
|
||
trace_event=[event-list]
|
||
[FTRACE] Set and start specified trace events in order
|
||
to facilitate early boot debugging. The event-list is a
|
||
comma-separated list of trace events to enable. See
|
||
also Documentation/trace/events.rst
|
||
|
||
trace_instance=[instance-info]
|
||
[FTRACE] Create a ring buffer instance early in boot up.
|
||
This will be listed in:
|
||
|
||
/sys/kernel/tracing/instances
|
||
|
||
Events can be enabled at the time the instance is created
|
||
via:
|
||
|
||
trace_instance=<name>,<system1>:<event1>,<system2>:<event2>
|
||
|
||
Note, the "<system*>:" portion is optional if the event is
|
||
unique.
|
||
|
||
trace_instance=foo,sched:sched_switch,irq_handler_entry,initcall
|
||
|
||
will enable the "sched_switch" event (note, the "sched:" is optional, and
|
||
the same thing would happen if it was left off). The irq_handler_entry
|
||
event, and all events under the "initcall" system.
|
||
|
||
Flags can be added to the instance to modify its behavior when it is
|
||
created. The flags are separated by '^'.
|
||
|
||
The available flags are:
|
||
|
||
traceoff - Have the tracing instance tracing disabled after it is created.
|
||
traceprintk - Have trace_printk() write into this trace instance
|
||
(note, "printk" and "trace_printk" can also be used)
|
||
|
||
trace_instance=foo^traceoff^traceprintk,sched,irq
|
||
|
||
The flags must come before the defined events.
|
||
|
||
If memory has been reserved (see memmap for x86), the instance
|
||
can use that memory:
|
||
|
||
memmap=12M$0x284500000 trace_instance=boot_map@0x284500000:12M
|
||
|
||
The above will create a "boot_map" instance that uses the physical
|
||
memory at 0x284500000 that is 12Megs. The per CPU buffers of that
|
||
instance will be split up accordingly.
|
||
|
||
Alternatively, the memory can be reserved by the reserve_mem option:
|
||
|
||
reserve_mem=12M:4096:trace trace_instance=boot_map@trace
|
||
|
||
This will reserve 12 megabytes at boot up with a 4096 byte alignment
|
||
and place the ring buffer in this memory. Note that due to KASLR, the
|
||
memory may not be the same location each time, which will not preserve
|
||
the buffer content.
|
||
|
||
Also note that the layout of the ring buffer data may change between
|
||
kernel versions where the validator will fail and reset the ring buffer
|
||
if the layout is not the same as the previous kernel.
|
||
|
||
If the ring buffer is used for persistent bootups and has events enabled,
|
||
it is recommend to disable tracing so that events from a previous boot do not
|
||
mix with events of the current boot (unless you are debugging a random crash
|
||
at boot up).
|
||
|
||
reserve_mem=12M:4096:trace trace_instance=boot_map^traceoff^traceprintk@trace,sched,irq
|
||
|
||
See also Documentation/trace/debugging.rst
|
||
|
||
|
||
trace_options=[option-list]
|
||
[FTRACE] Enable or disable tracer options at boot.
|
||
The option-list is a comma delimited list of options
|
||
that can be enabled or disabled just as if you were
|
||
to echo the option name into
|
||
|
||
/sys/kernel/tracing/trace_options
|
||
|
||
For example, to enable stacktrace option (to dump the
|
||
stack trace of each event), add to the command line:
|
||
|
||
trace_options=stacktrace
|
||
|
||
See also Documentation/trace/ftrace.rst "trace options"
|
||
section.
|
||
|
||
trace_trigger=[trigger-list]
|
||
[FTRACE] Add a event trigger on specific events.
|
||
Set a trigger on top of a specific event, with an optional
|
||
filter.
|
||
|
||
The format is is "trace_trigger=<event>.<trigger>[ if <filter>],..."
|
||
Where more than one trigger may be specified that are comma deliminated.
|
||
|
||
For example:
|
||
|
||
trace_trigger="sched_switch.stacktrace if prev_state == 2"
|
||
|
||
The above will enable the "stacktrace" trigger on the "sched_switch"
|
||
event but only trigger it if the "prev_state" of the "sched_switch"
|
||
event is "2" (TASK_UNINTERUPTIBLE).
|
||
|
||
See also "Event triggers" in Documentation/trace/events.rst
|
||
|
||
|
||
traceoff_on_warning
|
||
[FTRACE] enable this option to disable tracing when a
|
||
warning is hit. This turns off "tracing_on". Tracing can
|
||
be enabled again by echoing '1' into the "tracing_on"
|
||
file located in /sys/kernel/tracing/
|
||
|
||
This option is useful, as it disables the trace before
|
||
the WARNING dump is called, which prevents the trace to
|
||
be filled with content caused by the warning output.
|
||
|
||
This option can also be set at run time via the sysctl
|
||
option: kernel/traceoff_on_warning
|
||
|
||
transparent_hugepage=
|
||
[KNL]
|
||
Format: [always|madvise|never]
|
||
Can be used to control the default behavior of the system
|
||
with respect to transparent hugepages.
|
||
See Documentation/admin-guide/mm/transhuge.rst
|
||
for more details.
|
||
|
||
trusted.source= [KEYS]
|
||
Format: <string>
|
||
This parameter identifies the trust source as a backend
|
||
for trusted keys implementation. Supported trust
|
||
sources:
|
||
- "tpm"
|
||
- "tee"
|
||
- "caam"
|
||
- "dcp"
|
||
If not specified then it defaults to iterating through
|
||
the trust source list starting with TPM and assigns the
|
||
first trust source as a backend which is initialized
|
||
successfully during iteration.
|
||
|
||
trusted.rng= [KEYS]
|
||
Format: <string>
|
||
The RNG used to generate key material for trusted keys.
|
||
Can be one of:
|
||
- "kernel"
|
||
- the same value as trusted.source: "tpm" or "tee"
|
||
- "default"
|
||
If not specified, "default" is used. In this case,
|
||
the RNG's choice is left to each individual trust source.
|
||
|
||
trusted.dcp_use_otp_key
|
||
This is intended to be used in combination with
|
||
trusted.source=dcp and will select the DCP OTP key
|
||
instead of the DCP UNIQUE key blob encryption.
|
||
|
||
trusted.dcp_skip_zk_test
|
||
This is intended to be used in combination with
|
||
trusted.source=dcp and will disable the check if the
|
||
blob key is all zeros. This is helpful for situations where
|
||
having this key zero'ed is acceptable. E.g. in testing
|
||
scenarios.
|
||
|
||
tsc= Disable clocksource stability checks for TSC.
|
||
Format: <string>
|
||
[x86] reliable: mark tsc clocksource as reliable, this
|
||
disables clocksource verification at runtime, as well
|
||
as the stability checks done at bootup. Used to enable
|
||
high-resolution timer mode on older hardware, and in
|
||
virtualized environment.
|
||
[x86] noirqtime: Do not use TSC to do irq accounting.
|
||
Used to run time disable IRQ_TIME_ACCOUNTING on any
|
||
platforms where RDTSC is slow and this accounting
|
||
can add overhead.
|
||
[x86] unstable: mark the TSC clocksource as unstable, this
|
||
marks the TSC unconditionally unstable at bootup and
|
||
avoids any further wobbles once the TSC watchdog notices.
|
||
[x86] nowatchdog: disable clocksource watchdog. Used
|
||
in situations with strict latency requirements (where
|
||
interruptions from clocksource watchdog are not
|
||
acceptable).
|
||
[x86] recalibrate: force recalibration against a HW timer
|
||
(HPET or PM timer) on systems whose TSC frequency was
|
||
obtained from HW or FW using either an MSR or CPUID(0x15).
|
||
Warn if the difference is more than 500 ppm.
|
||
[x86] watchdog: Use TSC as the watchdog clocksource with
|
||
which to check other HW timers (HPET or PM timer), but
|
||
only on systems where TSC has been deemed trustworthy.
|
||
This will be suppressed by an earlier tsc=nowatchdog and
|
||
can be overridden by a later tsc=nowatchdog. A console
|
||
message will flag any such suppression or overriding.
|
||
|
||
tsc_early_khz= [X86,EARLY] Skip early TSC calibration and use the given
|
||
value instead. Useful when the early TSC frequency discovery
|
||
procedure is not reliable, such as on overclocked systems
|
||
with CPUID.16h support and partial CPUID.15h support.
|
||
Format: <unsigned int>
|
||
|
||
tsx= [X86] Control Transactional Synchronization
|
||
Extensions (TSX) feature in Intel processors that
|
||
support TSX control.
|
||
|
||
This parameter controls the TSX feature. The options are:
|
||
|
||
on - Enable TSX on the system. Although there are
|
||
mitigations for all known security vulnerabilities,
|
||
TSX has been known to be an accelerator for
|
||
several previous speculation-related CVEs, and
|
||
so there may be unknown security risks associated
|
||
with leaving it enabled.
|
||
|
||
off - Disable TSX on the system. (Note that this
|
||
option takes effect only on newer CPUs which are
|
||
not vulnerable to MDS, i.e., have
|
||
MSR_IA32_ARCH_CAPABILITIES.MDS_NO=1 and which get
|
||
the new IA32_TSX_CTRL MSR through a microcode
|
||
update. This new MSR allows for the reliable
|
||
deactivation of the TSX functionality.)
|
||
|
||
auto - Disable TSX if X86_BUG_TAA is present,
|
||
otherwise enable TSX on the system.
|
||
|
||
Not specifying this option is equivalent to tsx=off.
|
||
|
||
See Documentation/admin-guide/hw-vuln/tsx_async_abort.rst
|
||
for more details.
|
||
|
||
tsx_async_abort= [X86,INTEL,EARLY] Control mitigation for the TSX Async
|
||
Abort (TAA) vulnerability.
|
||
|
||
Similar to Micro-architectural Data Sampling (MDS)
|
||
certain CPUs that support Transactional
|
||
Synchronization Extensions (TSX) are vulnerable to an
|
||
exploit against CPU internal buffers which can forward
|
||
information to a disclosure gadget under certain
|
||
conditions.
|
||
|
||
In vulnerable processors, the speculatively forwarded
|
||
data can be used in a cache side channel attack, to
|
||
access data to which the attacker does not have direct
|
||
access.
|
||
|
||
This parameter controls the TAA mitigation. The
|
||
options are:
|
||
|
||
full - Enable TAA mitigation on vulnerable CPUs
|
||
if TSX is enabled.
|
||
|
||
full,nosmt - Enable TAA mitigation and disable SMT on
|
||
vulnerable CPUs. If TSX is disabled, SMT
|
||
is not disabled because CPU is not
|
||
vulnerable to cross-thread TAA attacks.
|
||
off - Unconditionally disable TAA mitigation
|
||
|
||
On MDS-affected machines, tsx_async_abort=off can be
|
||
prevented by an active MDS mitigation as both vulnerabilities
|
||
are mitigated with the same mechanism so in order to disable
|
||
this mitigation, you need to specify mds=off too.
|
||
|
||
Not specifying this option is equivalent to
|
||
tsx_async_abort=full. On CPUs which are MDS affected
|
||
and deploy MDS mitigation, TAA mitigation is not
|
||
required and doesn't provide any additional
|
||
mitigation.
|
||
|
||
For details see:
|
||
Documentation/admin-guide/hw-vuln/tsx_async_abort.rst
|
||
|
||
turbografx.map[2|3]= [HW,JOY]
|
||
TurboGraFX parallel port interface
|
||
Format:
|
||
<port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
|
||
See also Documentation/input/devices/joystick-parport.rst
|
||
|
||
udbg-immortal [PPC] When debugging early kernel crashes that
|
||
happen after console_init() and before a proper
|
||
console driver takes over, this boot options might
|
||
help "seeing" what's going on.
|
||
|
||
uhash_entries= [KNL,NET]
|
||
Set number of hash buckets for UDP/UDP-Lite connections
|
||
|
||
uhci-hcd.ignore_oc=
|
||
[USB] Ignore overcurrent events (default N).
|
||
Some badly-designed motherboards generate lots of
|
||
bogus events, for ports that aren't wired to
|
||
anything. Set this parameter to avoid log spamming.
|
||
Note that genuine overcurrent events won't be
|
||
reported either.
|
||
|
||
unknown_nmi_panic
|
||
[X86] Cause panic on unknown NMI.
|
||
|
||
unwind_debug [X86-64,EARLY]
|
||
Enable unwinder debug output. This can be
|
||
useful for debugging certain unwinder error
|
||
conditions, including corrupt stacks and
|
||
bad/missing unwinder metadata.
|
||
|
||
usbcore.authorized_default=
|
||
[USB] Default USB device authorization:
|
||
(default -1 = authorized (same as 1),
|
||
0 = not authorized, 1 = authorized, 2 = authorized
|
||
if device connected to internal port)
|
||
|
||
usbcore.autosuspend=
|
||
[USB] The autosuspend time delay (in seconds) used
|
||
for newly-detected USB devices (default 2). This
|
||
is the time required before an idle device will be
|
||
autosuspended. Devices for which the delay is set
|
||
to a negative value won't be autosuspended at all.
|
||
|
||
usbcore.usbfs_snoop=
|
||
[USB] Set to log all usbfs traffic (default 0 = off).
|
||
|
||
usbcore.usbfs_snoop_max=
|
||
[USB] Maximum number of bytes to snoop in each URB
|
||
(default = 65536).
|
||
|
||
usbcore.blinkenlights=
|
||
[USB] Set to cycle leds on hubs (default 0 = off).
|
||
|
||
usbcore.old_scheme_first=
|
||
[USB] Start with the old device initialization
|
||
scheme (default 0 = off).
|
||
|
||
usbcore.usbfs_memory_mb=
|
||
[USB] Memory limit (in MB) for buffers allocated by
|
||
usbfs (default = 16, 0 = max = 2047).
|
||
|
||
usbcore.use_both_schemes=
|
||
[USB] Try the other device initialization scheme
|
||
if the first one fails (default 1 = enabled).
|
||
|
||
usbcore.initial_descriptor_timeout=
|
||
[USB] Specifies timeout for the initial 64-byte
|
||
USB_REQ_GET_DESCRIPTOR request in milliseconds
|
||
(default 5000 = 5.0 seconds).
|
||
|
||
usbcore.nousb [USB] Disable the USB subsystem
|
||
|
||
usbcore.quirks=
|
||
[USB] A list of quirk entries to augment the built-in
|
||
usb core quirk list. List entries are separated by
|
||
commas. Each entry has the form
|
||
VendorID:ProductID:Flags. The IDs are 4-digit hex
|
||
numbers and Flags is a set of letters. Each letter
|
||
will change the built-in quirk; setting it if it is
|
||
clear and clearing it if it is set. The letters have
|
||
the following meanings:
|
||
a = USB_QUIRK_STRING_FETCH_255 (string
|
||
descriptors must not be fetched using
|
||
a 255-byte read);
|
||
b = USB_QUIRK_RESET_RESUME (device can't resume
|
||
correctly so reset it instead);
|
||
c = USB_QUIRK_NO_SET_INTF (device can't handle
|
||
Set-Interface requests);
|
||
d = USB_QUIRK_CONFIG_INTF_STRINGS (device can't
|
||
handle its Configuration or Interface
|
||
strings);
|
||
e = USB_QUIRK_RESET (device can't be reset
|
||
(e.g morph devices), don't use reset);
|
||
f = USB_QUIRK_HONOR_BNUMINTERFACES (device has
|
||
more interface descriptions than the
|
||
bNumInterfaces count, and can't handle
|
||
talking to these interfaces);
|
||
g = USB_QUIRK_DELAY_INIT (device needs a pause
|
||
during initialization, after we read
|
||
the device descriptor);
|
||
h = USB_QUIRK_LINEAR_UFRAME_INTR_BINTERVAL (For
|
||
high speed and super speed interrupt
|
||
endpoints, the USB 2.0 and USB 3.0 spec
|
||
require the interval in microframes (1
|
||
microframe = 125 microseconds) to be
|
||
calculated as interval = 2 ^
|
||
(bInterval-1).
|
||
Devices with this quirk report their
|
||
bInterval as the result of this
|
||
calculation instead of the exponent
|
||
variable used in the calculation);
|
||
i = USB_QUIRK_DEVICE_QUALIFIER (device can't
|
||
handle device_qualifier descriptor
|
||
requests);
|
||
j = USB_QUIRK_IGNORE_REMOTE_WAKEUP (device
|
||
generates spurious wakeup, ignore
|
||
remote wakeup capability);
|
||
k = USB_QUIRK_NO_LPM (device can't handle Link
|
||
Power Management);
|
||
l = USB_QUIRK_LINEAR_FRAME_INTR_BINTERVAL
|
||
(Device reports its bInterval as linear
|
||
frames instead of the USB 2.0
|
||
calculation);
|
||
m = USB_QUIRK_DISCONNECT_SUSPEND (Device needs
|
||
to be disconnected before suspend to
|
||
prevent spurious wakeup);
|
||
n = USB_QUIRK_DELAY_CTRL_MSG (Device needs a
|
||
pause after every control message);
|
||
o = USB_QUIRK_HUB_SLOW_RESET (Hub needs extra
|
||
delay after resetting its port);
|
||
p = USB_QUIRK_SHORT_SET_ADDRESS_REQ_TIMEOUT
|
||
(Reduce timeout of the SET_ADDRESS
|
||
request from 5000 ms to 500 ms);
|
||
Example: quirks=0781:5580:bk,0a5c:5834:gij
|
||
|
||
usbhid.mousepoll=
|
||
[USBHID] The interval which mice are to be polled at.
|
||
|
||
usbhid.jspoll=
|
||
[USBHID] The interval which joysticks are to be polled at.
|
||
|
||
usbhid.kbpoll=
|
||
[USBHID] The interval which keyboards are to be polled at.
|
||
|
||
usb-storage.delay_use=
|
||
[UMS] The delay in seconds before a new device is
|
||
scanned for Logical Units (default 1).
|
||
Optionally the delay in milliseconds if the value has
|
||
suffix with "ms".
|
||
Example: delay_use=2567ms
|
||
|
||
usb-storage.quirks=
|
||
[UMS] A list of quirks entries to supplement or
|
||
override the built-in unusual_devs list. List
|
||
entries are separated by commas. Each entry has
|
||
the form VID:PID:Flags where VID and PID are Vendor
|
||
and Product ID values (4-digit hex numbers) and
|
||
Flags is a set of characters, each corresponding
|
||
to a common usb-storage quirk flag as follows:
|
||
a = SANE_SENSE (collect more than 18 bytes
|
||
of sense data, not on uas);
|
||
b = BAD_SENSE (don't collect more than 18
|
||
bytes of sense data, not on uas);
|
||
c = FIX_CAPACITY (decrease the reported
|
||
device capacity by one sector);
|
||
d = NO_READ_DISC_INFO (don't use
|
||
READ_DISC_INFO command, not on uas);
|
||
e = NO_READ_CAPACITY_16 (don't use
|
||
READ_CAPACITY_16 command);
|
||
f = NO_REPORT_OPCODES (don't use report opcodes
|
||
command, uas only);
|
||
g = MAX_SECTORS_240 (don't transfer more than
|
||
240 sectors at a time, uas only);
|
||
h = CAPACITY_HEURISTICS (decrease the
|
||
reported device capacity by one
|
||
sector if the number is odd);
|
||
i = IGNORE_DEVICE (don't bind to this
|
||
device);
|
||
j = NO_REPORT_LUNS (don't use report luns
|
||
command, uas only);
|
||
k = NO_SAME (do not use WRITE_SAME, uas only)
|
||
l = NOT_LOCKABLE (don't try to lock and
|
||
unlock ejectable media, not on uas);
|
||
m = MAX_SECTORS_64 (don't transfer more
|
||
than 64 sectors = 32 KB at a time,
|
||
not on uas);
|
||
n = INITIAL_READ10 (force a retry of the
|
||
initial READ(10) command, not on uas);
|
||
o = CAPACITY_OK (accept the capacity
|
||
reported by the device, not on uas);
|
||
p = WRITE_CACHE (the device cache is ON
|
||
by default, not on uas);
|
||
r = IGNORE_RESIDUE (the device reports
|
||
bogus residue values, not on uas);
|
||
s = SINGLE_LUN (the device has only one
|
||
Logical Unit);
|
||
t = NO_ATA_1X (don't allow ATA(12) and ATA(16)
|
||
commands, uas only);
|
||
u = IGNORE_UAS (don't bind to the uas driver);
|
||
w = NO_WP_DETECT (don't test whether the
|
||
medium is write-protected).
|
||
y = ALWAYS_SYNC (issue a SYNCHRONIZE_CACHE
|
||
even if the device claims no cache,
|
||
not on uas)
|
||
Example: quirks=0419:aaf5:rl,0421:0433:rc
|
||
|
||
user_debug= [KNL,ARM]
|
||
Format: <int>
|
||
See arch/arm/Kconfig.debug help text.
|
||
1 - undefined instruction events
|
||
2 - system calls
|
||
4 - invalid data aborts
|
||
8 - SIGSEGV faults
|
||
16 - SIGBUS faults
|
||
Example: user_debug=31
|
||
|
||
userpte=
|
||
[X86,EARLY] Flags controlling user PTE allocations.
|
||
|
||
nohigh = do not allocate PTE pages in
|
||
HIGHMEM regardless of setting
|
||
of CONFIG_HIGHPTE.
|
||
|
||
vdso= [X86,SH,SPARC]
|
||
On X86_32, this is an alias for vdso32=. Otherwise:
|
||
|
||
vdso=1: enable VDSO (the default)
|
||
vdso=0: disable VDSO mapping
|
||
|
||
vdso32= [X86] Control the 32-bit vDSO
|
||
vdso32=1: enable 32-bit VDSO
|
||
vdso32=0 or vdso32=2: disable 32-bit VDSO
|
||
|
||
See the help text for CONFIG_COMPAT_VDSO for more
|
||
details. If CONFIG_COMPAT_VDSO is set, the default is
|
||
vdso32=0; otherwise, the default is vdso32=1.
|
||
|
||
For compatibility with older kernels, vdso32=2 is an
|
||
alias for vdso32=0.
|
||
|
||
Try vdso32=0 if you encounter an error that says:
|
||
dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
|
||
|
||
video= [FB,EARLY] Frame buffer configuration
|
||
See Documentation/fb/modedb.rst.
|
||
|
||
video.brightness_switch_enabled= [ACPI]
|
||
Format: [0|1]
|
||
If set to 1, on receiving an ACPI notify event
|
||
generated by hotkey, video driver will adjust brightness
|
||
level and then send out the event to user space through
|
||
the allocated input device. If set to 0, video driver
|
||
will only send out the event without touching backlight
|
||
brightness level.
|
||
default: 1
|
||
|
||
virtio_mmio.device=
|
||
[VMMIO] Memory mapped virtio (platform) device.
|
||
|
||
<size>@<baseaddr>:<irq>[:<id>]
|
||
where:
|
||
<size> := size (can use standard suffixes
|
||
like K, M and G)
|
||
<baseaddr> := physical base address
|
||
<irq> := interrupt number (as passed to
|
||
request_irq())
|
||
<id> := (optional) platform device id
|
||
example:
|
||
virtio_mmio.device=1K@0x100b0000:48:7
|
||
|
||
Can be used multiple times for multiple devices.
|
||
|
||
vga= [BOOT,X86-32] Select a particular video mode
|
||
See Documentation/arch/x86/boot.rst and
|
||
Documentation/admin-guide/svga.rst.
|
||
Use vga=ask for menu.
|
||
This is actually a boot loader parameter; the value is
|
||
passed to the kernel using a special protocol.
|
||
|
||
vm_debug[=options] [KNL] Available with CONFIG_DEBUG_VM=y.
|
||
May slow down system boot speed, especially when
|
||
enabled on systems with a large amount of memory.
|
||
All options are enabled by default, and this
|
||
interface is meant to allow for selectively
|
||
enabling or disabling specific virtual memory
|
||
debugging features.
|
||
|
||
Available options are:
|
||
P Enable page structure init time poisoning
|
||
- Disable all of the above options
|
||
|
||
vmalloc=nn[KMG] [KNL,BOOT,EARLY] Forces the vmalloc area to have an
|
||
exact size of <nn>. This can be used to increase
|
||
the minimum size (128MB on x86, arm32 platforms).
|
||
It can also be used to decrease the size and leave more room
|
||
for directly mapped kernel RAM. Note that this parameter does
|
||
not exist on many other platforms (including arm64, alpha,
|
||
loongarch, arc, csky, hexagon, microblaze, mips, nios2, openrisc,
|
||
parisc, m64k, powerpc, riscv, sh, um, xtensa, s390, sparc).
|
||
|
||
vmcp_cma=nn[MG] [KNL,S390,EARLY]
|
||
Sets the memory size reserved for contiguous memory
|
||
allocations for the vmcp device driver.
|
||
|
||
vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
|
||
Format: <command>
|
||
|
||
vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
|
||
Format: <command>
|
||
|
||
vmpoff= [KNL,S390] Perform z/VM CP command after power off.
|
||
Format: <command>
|
||
|
||
vsyscall= [X86-64,EARLY]
|
||
Controls the behavior of vsyscalls (i.e. calls to
|
||
fixed addresses of 0xffffffffff600x00 from legacy
|
||
code). Most statically-linked binaries and older
|
||
versions of glibc use these calls. Because these
|
||
functions are at fixed addresses, they make nice
|
||
targets for exploits that can control RIP.
|
||
|
||
emulate Vsyscalls turn into traps and are emulated
|
||
reasonably safely. The vsyscall page is
|
||
readable.
|
||
|
||
xonly [default] Vsyscalls turn into traps and are
|
||
emulated reasonably safely. The vsyscall
|
||
page is not readable.
|
||
|
||
none Vsyscalls don't work at all. This makes
|
||
them quite hard to use for exploits but
|
||
might break your system.
|
||
|
||
vt.color= [VT] Default text color.
|
||
Format: 0xYX, X = foreground, Y = background.
|
||
Default: 0x07 = light gray on black.
|
||
|
||
vt.cur_default= [VT] Default cursor shape.
|
||
Format: 0xCCBBAA, where AA, BB, and CC are the same as
|
||
the parameters of the <Esc>[?A;B;Cc escape sequence;
|
||
see VGA-softcursor.txt. Default: 2 = underline.
|
||
|
||
vt.default_blu= [VT]
|
||
Format: <blue0>,<blue1>,<blue2>,...,<blue15>
|
||
Change the default blue palette of the console.
|
||
This is a 16-member array composed of values
|
||
ranging from 0-255.
|
||
|
||
vt.default_grn= [VT]
|
||
Format: <green0>,<green1>,<green2>,...,<green15>
|
||
Change the default green palette of the console.
|
||
This is a 16-member array composed of values
|
||
ranging from 0-255.
|
||
|
||
vt.default_red= [VT]
|
||
Format: <red0>,<red1>,<red2>,...,<red15>
|
||
Change the default red palette of the console.
|
||
This is a 16-member array composed of values
|
||
ranging from 0-255.
|
||
|
||
vt.default_utf8=
|
||
[VT]
|
||
Format=<0|1>
|
||
Set system-wide default UTF-8 mode for all tty's.
|
||
Default is 1, i.e. UTF-8 mode is enabled for all
|
||
newly opened terminals.
|
||
|
||
vt.global_cursor_default=
|
||
[VT]
|
||
Format=<-1|0|1>
|
||
Set system-wide default for whether a cursor
|
||
is shown on new VTs. Default is -1,
|
||
i.e. cursors will be created by default unless
|
||
overridden by individual drivers. 0 will hide
|
||
cursors, 1 will display them.
|
||
|
||
vt.italic= [VT] Default color for italic text; 0-15.
|
||
Default: 2 = green.
|
||
|
||
vt.underline= [VT] Default color for underlined text; 0-15.
|
||
Default: 3 = cyan.
|
||
|
||
watchdog timers [HW,WDT] For information on watchdog timers,
|
||
see Documentation/watchdog/watchdog-parameters.rst
|
||
or other driver-specific files in the
|
||
Documentation/watchdog/ directory.
|
||
|
||
watchdog_thresh=
|
||
[KNL]
|
||
Set the hard lockup detector stall duration
|
||
threshold in seconds. The soft lockup detector
|
||
threshold is set to twice the value. A value of 0
|
||
disables both lockup detectors. Default is 10
|
||
seconds.
|
||
|
||
workqueue.unbound_cpus=
|
||
[KNL,SMP] Specify to constrain one or some CPUs
|
||
to use in unbound workqueues.
|
||
Format: <cpu-list>
|
||
By default, all online CPUs are available for
|
||
unbound workqueues.
|
||
|
||
workqueue.watchdog_thresh=
|
||
If CONFIG_WQ_WATCHDOG is configured, workqueue can
|
||
warn stall conditions and dump internal state to
|
||
help debugging. 0 disables workqueue stall
|
||
detection; otherwise, it's the stall threshold
|
||
duration in seconds. The default value is 30 and
|
||
it can be updated at runtime by writing to the
|
||
corresponding sysfs file.
|
||
|
||
workqueue.panic_on_stall=<uint>
|
||
Panic when workqueue stall is detected by
|
||
CONFIG_WQ_WATCHDOG. It sets the number times of the
|
||
stall to trigger panic.
|
||
|
||
The default is 0, which disables the panic on stall.
|
||
|
||
workqueue.cpu_intensive_thresh_us=
|
||
Per-cpu work items which run for longer than this
|
||
threshold are automatically considered CPU intensive
|
||
and excluded from concurrency management to prevent
|
||
them from noticeably delaying other per-cpu work
|
||
items. Default is 10000 (10ms).
|
||
|
||
If CONFIG_WQ_CPU_INTENSIVE_REPORT is set, the kernel
|
||
will report the work functions which violate this
|
||
threshold repeatedly. They are likely good
|
||
candidates for using WQ_UNBOUND workqueues instead.
|
||
|
||
workqueue.cpu_intensive_warning_thresh=<uint>
|
||
If CONFIG_WQ_CPU_INTENSIVE_REPORT is set, the kernel
|
||
will report the work functions which violate the
|
||
intensive_threshold_us repeatedly. In order to prevent
|
||
spurious warnings, start printing only after a work
|
||
function has violated this threshold number of times.
|
||
|
||
The default is 4 times. 0 disables the warning.
|
||
|
||
workqueue.power_efficient
|
||
Per-cpu workqueues are generally preferred because
|
||
they show better performance thanks to cache
|
||
locality; unfortunately, per-cpu workqueues tend to
|
||
be more power hungry than unbound workqueues.
|
||
|
||
Enabling this makes the per-cpu workqueues which
|
||
were observed to contribute significantly to power
|
||
consumption unbound, leading to measurably lower
|
||
power usage at the cost of small performance
|
||
overhead.
|
||
|
||
The default value of this parameter is determined by
|
||
the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
|
||
|
||
workqueue.default_affinity_scope=
|
||
Select the default affinity scope to use for unbound
|
||
workqueues. Can be one of "cpu", "smt", "cache",
|
||
"numa" and "system". Default is "cache". For more
|
||
information, see the Affinity Scopes section in
|
||
Documentation/core-api/workqueue.rst.
|
||
|
||
This can be changed after boot by writing to the
|
||
matching /sys/module/workqueue/parameters file. All
|
||
workqueues with the "default" affinity scope will be
|
||
updated accordingly.
|
||
|
||
workqueue.debug_force_rr_cpu
|
||
Workqueue used to implicitly guarantee that work
|
||
items queued without explicit CPU specified are put
|
||
on the local CPU. This guarantee is no longer true
|
||
and while local CPU is still preferred work items
|
||
may be put on foreign CPUs. This debug option
|
||
forces round-robin CPU selection to flush out
|
||
usages which depend on the now broken guarantee.
|
||
When enabled, memory and cache locality will be
|
||
impacted.
|
||
|
||
writecombine= [LOONGARCH,EARLY] Control the MAT (Memory Access
|
||
Type) of ioremap_wc().
|
||
|
||
on - Enable writecombine, use WUC for ioremap_wc()
|
||
off - Disable writecombine, use SUC for ioremap_wc()
|
||
|
||
x2apic_phys [X86-64,APIC,EARLY] Use x2apic physical mode instead of
|
||
default x2apic cluster mode on platforms
|
||
supporting x2apic.
|
||
|
||
xen_512gb_limit [KNL,X86-64,XEN]
|
||
Restricts the kernel running paravirtualized under Xen
|
||
to use only up to 512 GB of RAM. The reason to do so is
|
||
crash analysis tools and Xen tools for doing domain
|
||
save/restore/migration must be enabled to handle larger
|
||
domains.
|
||
|
||
xen_emul_unplug= [HW,X86,XEN,EARLY]
|
||
Unplug Xen emulated devices
|
||
Format: [unplug0,][unplug1]
|
||
ide-disks -- unplug primary master IDE devices
|
||
aux-ide-disks -- unplug non-primary-master IDE devices
|
||
nics -- unplug network devices
|
||
all -- unplug all emulated devices (NICs and IDE disks)
|
||
unnecessary -- unplugging emulated devices is
|
||
unnecessary even if the host did not respond to
|
||
the unplug protocol
|
||
never -- do not unplug even if version check succeeds
|
||
|
||
xen_legacy_crash [X86,XEN,EARLY]
|
||
Crash from Xen panic notifier, without executing late
|
||
panic() code such as dumping handler.
|
||
|
||
xen_mc_debug [X86,XEN,EARLY]
|
||
Enable multicall debugging when running as a Xen PV guest.
|
||
Enabling this feature will reduce performance a little
|
||
bit, so it should only be enabled for obtaining extended
|
||
debug data in case of multicall errors.
|
||
|
||
xen_msr_safe= [X86,XEN,EARLY]
|
||
Format: <bool>
|
||
Select whether to always use non-faulting (safe) MSR
|
||
access functions when running as Xen PV guest. The
|
||
default value is controlled by CONFIG_XEN_PV_MSR_SAFE.
|
||
|
||
xen_nopv [X86]
|
||
Disables the PV optimizations forcing the HVM guest to
|
||
run as generic HVM guest with no PV drivers.
|
||
This option is obsoleted by the "nopv" option, which
|
||
has equivalent effect for XEN platform.
|
||
|
||
xen_no_vector_callback
|
||
[KNL,X86,XEN,EARLY] Disable the vector callback for Xen
|
||
event channel interrupts.
|
||
|
||
xen_scrub_pages= [XEN]
|
||
Boolean option to control scrubbing pages before giving them back
|
||
to Xen, for use by other domains. Can be also changed at runtime
|
||
with /sys/devices/system/xen_memory/xen_memory0/scrub_pages.
|
||
Default value controlled with CONFIG_XEN_SCRUB_PAGES_DEFAULT.
|
||
|
||
xen_timer_slop= [X86-64,XEN,EARLY]
|
||
Set the timer slop (in nanoseconds) for the virtual Xen
|
||
timers (default is 100000). This adjusts the minimum
|
||
delta of virtualized Xen timers, where lower values
|
||
improve timer resolution at the expense of processing
|
||
more timer interrupts.
|
||
|
||
xen.balloon_boot_timeout= [XEN]
|
||
The time (in seconds) to wait before giving up to boot
|
||
in case initial ballooning fails to free enough memory.
|
||
Applies only when running as HVM or PVH guest and
|
||
started with less memory configured than allowed at
|
||
max. Default is 180.
|
||
|
||
xen.event_eoi_delay= [XEN]
|
||
How long to delay EOI handling in case of event
|
||
storms (jiffies). Default is 10.
|
||
|
||
xen.event_loop_timeout= [XEN]
|
||
After which time (jiffies) the event handling loop
|
||
should start to delay EOI handling. Default is 2.
|
||
|
||
xen.fifo_events= [XEN]
|
||
Boolean parameter to disable using fifo event handling
|
||
even if available. Normally fifo event handling is
|
||
preferred over the 2-level event handling, as it is
|
||
fairer and the number of possible event channels is
|
||
much higher. Default is on (use fifo events).
|
||
|
||
xirc2ps_cs= [NET,PCMCIA]
|
||
Format:
|
||
<irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
|
||
|
||
xive= [PPC]
|
||
By default on POWER9 and above, the kernel will
|
||
natively use the XIVE interrupt controller. This option
|
||
allows the fallback firmware mode to be used:
|
||
|
||
off Fallback to firmware control of XIVE interrupt
|
||
controller on both pseries and powernv
|
||
platforms. Only useful on POWER9 and above.
|
||
|
||
xive.store-eoi=off [PPC]
|
||
By default on POWER10 and above, the kernel will use
|
||
stores for EOI handling when the XIVE interrupt mode
|
||
is active. This option allows the XIVE driver to use
|
||
loads instead, as on POWER9.
|
||
|
||
xhci-hcd.quirks [USB,KNL]
|
||
A hex value specifying bitmask with supplemental xhci
|
||
host controller quirks. Meaning of each bit can be
|
||
consulted in header drivers/usb/host/xhci.h.
|
||
|
||
xmon [PPC,EARLY]
|
||
Format: { early | on | rw | ro | off }
|
||
Controls if xmon debugger is enabled. Default is off.
|
||
Passing only "xmon" is equivalent to "xmon=early".
|
||
early Call xmon as early as possible on boot; xmon
|
||
debugger is called from setup_arch().
|
||
on xmon debugger hooks will be installed so xmon
|
||
is only called on a kernel crash. Default mode,
|
||
i.e. either "ro" or "rw" mode, is controlled
|
||
with CONFIG_XMON_DEFAULT_RO_MODE.
|
||
rw xmon debugger hooks will be installed so xmon
|
||
is called only on a kernel crash, mode is write,
|
||
meaning SPR registers, memory and, other data
|
||
can be written using xmon commands.
|
||
ro same as "rw" option above but SPR registers,
|
||
memory, and other data can't be written using
|
||
xmon commands.
|
||
off xmon is disabled.
|