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powerpc/fadump: use FADump instead of fadump for how it is pronounced
fadump is pronounced f-a-dump. Update documentation accordingly. Also, update how fadump_region contents look like with recent changes. Signed-off-by: Hari Bathini <hbathini@linux.ibm.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/156821339317.5656.15852294223821732082.stgit@hbathini.in.ibm.com
This commit is contained in:
Hari Bathini
Michael Ellerman
parent
f35120115b
commit
1679b96e69
@ -9,18 +9,18 @@ a crashed system, and to do so from a fully-reset system, and
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to minimize the total elapsed time until the system is back
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in production use.
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- Firmware assisted dump (fadump) infrastructure is intended to replace
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- Firmware-Assisted Dump (FADump) infrastructure is intended to replace
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the existing phyp assisted dump.
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- Fadump uses the same firmware interfaces and memory reservation model
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as phyp assisted dump.
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- Unlike phyp dump, fadump exports the memory dump through /proc/vmcore
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- Unlike phyp dump, FADump exports the memory dump through /proc/vmcore
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in the ELF format in the same way as kdump. This helps us reuse the
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kdump infrastructure for dump capture and filtering.
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- Unlike phyp dump, userspace tool does not need to refer any sysfs
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interface while reading /proc/vmcore.
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- Unlike phyp dump, fadump allows user to release all the memory reserved
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- Unlike phyp dump, FADump allows user to release all the memory reserved
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for dump, with a single operation of echo 1 > /sys/kernel/fadump_release_mem.
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- Once enabled through kernel boot parameter, fadump can be
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- Once enabled through kernel boot parameter, FADump can be
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started/stopped through /sys/kernel/fadump_registered interface (see
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sysfs files section below) and can be easily integrated with kdump
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service start/stop init scripts.
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@ -34,7 +34,7 @@ dump offers several strong, practical advantages:
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in a clean, consistent state.
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- Once the dump is copied out, the memory that held the dump
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is immediately available to the running kernel. And therefore,
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unlike kdump, fadump doesn't need a 2nd reboot to get back
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unlike kdump, FADump doesn't need a 2nd reboot to get back
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the system to the production configuration.
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The above can only be accomplished by coordination with,
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@ -63,7 +63,7 @@ as follows:
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boot successfully. For syntax of crashkernel= parameter,
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refer to Documentation/admin-guide/kdump/kdump.rst. If any offset is
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provided in crashkernel= parameter, it will be ignored
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as fadump uses a predefined offset to reserve memory
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as FADump uses a predefined offset to reserve memory
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for boot memory dump preservation in case of a crash.
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- After the low memory (boot memory) area has been saved, the
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@ -123,7 +123,7 @@ blocking this significant chunk of memory from production kernel.
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Hence, the implementation uses the Linux kernel's Contiguous Memory
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Allocator (CMA) for memory reservation if CMA is configured for kernel.
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With CMA reservation this memory will be available for applications to
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use it, while kernel is prevented from using it. With this fadump will
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use it, while kernel is prevented from using it. With this FADump will
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still be able to capture all of the kernel memory and most of the user
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space memory except the user pages that were present in CMA region::
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@ -173,14 +173,14 @@ KDump, as dump mechanism.
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The tools to examine the dump will be same as the ones
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used for kdump.
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How to enable firmware-assisted dump (fadump):
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How to enable firmware-assisted dump (FADump):
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----------------------------------------------
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1. Set config option CONFIG_FA_DUMP=y and build kernel.
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2. Boot into linux kernel with 'fadump=on' kernel cmdline option.
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By default, fadump reserved memory will be initialized as CMA area.
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By default, FADump reserved memory will be initialized as CMA area.
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Alternatively, user can boot linux kernel with 'fadump=nocma' to
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prevent fadump to use CMA.
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prevent FADump to use CMA.
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3. Optionally, user can also set 'crashkernel=' kernel cmdline
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to specify size of the memory to reserve for boot memory dump
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preservation.
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@ -206,29 +206,29 @@ the control files and debugfs file to display memory reserved region.
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Here is the list of files under kernel sysfs:
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/sys/kernel/fadump_enabled
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This is used to display the fadump status.
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This is used to display the FADump status.
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- 0 = fadump is disabled
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- 1 = fadump is enabled
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- 0 = FADump is disabled
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- 1 = FADump is enabled
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This interface can be used by kdump init scripts to identify if
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fadump is enabled in the kernel and act accordingly.
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FADump is enabled in the kernel and act accordingly.
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/sys/kernel/fadump_registered
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This is used to display the fadump registration status as well
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as to control (start/stop) the fadump registration.
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This is used to display the FADump registration status as well
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as to control (start/stop) the FADump registration.
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- 0 = fadump is not registered.
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- 1 = fadump is registered and ready to handle system crash.
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- 0 = FADump is not registered.
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- 1 = FADump is registered and ready to handle system crash.
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To register fadump echo 1 > /sys/kernel/fadump_registered and
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To register FADump echo 1 > /sys/kernel/fadump_registered and
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echo 0 > /sys/kernel/fadump_registered for un-register and stop the
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fadump. Once the fadump is un-registered, the system crash will not
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FADump. Once the FADump is un-registered, the system crash will not
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be handled and vmcore will not be captured. This interface can be
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easily integrated with kdump service start/stop.
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/sys/kernel/fadump_release_mem
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This file is available only when fadump is active during
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This file is available only when FADump is active during
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second kernel. This is used to release the reserved memory
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region that are held for saving crash dump. To release the
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reserved memory echo 1 to it::
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@ -246,21 +246,25 @@ Here is the list of files under powerpc debugfs:
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(Assuming debugfs is mounted on /sys/kernel/debug directory.)
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/sys/kernel/debug/powerpc/fadump_region
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This file shows the reserved memory regions if fadump is
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This file shows the reserved memory regions if FADump is
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enabled otherwise this file is empty. The output format
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is::
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<region>: [<start>-<end>] <reserved-size> bytes, Dumped: <dump-size>
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and for kernel DUMP region is:
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DUMP: Src: <src-addr>, Dest: <dest-addr>, Size: <size>, Dumped: # bytes
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e.g.
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Contents when fadump is registered during first kernel::
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Contents when FADump is registered during first kernel::
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# cat /sys/kernel/debug/powerpc/fadump_region
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CPU : [0x0000006ffb0000-0x0000006fff001f] 0x40020 bytes, Dumped: 0x0
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HPTE: [0x0000006fff0020-0x0000006fff101f] 0x1000 bytes, Dumped: 0x0
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DUMP: [0x0000006fff1020-0x0000007fff101f] 0x10000000 bytes, Dumped: 0x0
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Contents when fadump is active during second kernel::
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Contents when FADump is active during second kernel::
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# cat /sys/kernel/debug/powerpc/fadump_region
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CPU : [0x0000006ffb0000-0x0000006fff001f] 0x40020 bytes, Dumped: 0x40020
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@ -268,6 +272,7 @@ Here is the list of files under powerpc debugfs:
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DUMP: [0x0000006fff1020-0x0000007fff101f] 0x10000000 bytes, Dumped: 0x10000000
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: [0x00000010000000-0x0000006ffaffff] 0x5ffb0000 bytes, Dumped: 0x5ffb0000
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NOTE:
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Please refer to Documentation/filesystems/debugfs.txt on
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how to mount the debugfs filesystem.
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@ -278,7 +283,7 @@ TODO:
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- Need to come up with the better approach to find out more
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accurate boot memory size that is required for a kernel to
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boot successfully when booted with restricted memory.
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- The fadump implementation introduces a fadump crash info structure
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- The FADump implementation introduces a FADump crash info structure
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in the scratch area before the ELF core header. The idea of introducing
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this structure is to pass some important crash info data to the second
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kernel which will help second kernel to populate ELF core header with
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