"prefetch", "prefault" and "speculative" are used throughout KVM to mean
the same thing. Use a single name, standardizing on "prefetch" which
is already used by various functions such as direct_pte_prefetch,
FNAME(prefetch_gpte), FNAME(pte_prefetch), etc.
Suggested-by: David Matlack <dmatlack@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Unify the flags for rmaps and page tracking data, using a
single flag in struct kvm_arch and a single loop to go
over all the address spaces and memslots. This avoids
code duplication between alloc_all_memslots_rmaps and
kvm_page_track_enable_mmu_write_tracking.
Signed-off-by: David Stevens <stevensd@chromium.org>
[This patch is the delta between David's v2 and v3, with conflicts
fixed and my own commit message. - Paolo]
Co-developed-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Since commit c300ab9f08 ("KVM: x86: Replace late check_nested_events() hack with
more precise fix") there is no longer the certainty that check_nested_events()
tries to inject an external interrupt vmexit to L1 on every call to vcpu_enter_guest.
Therefore, even in that case we need to set KVM_REQ_EVENT. This ensures
that inject_pending_event() is called, and from there kvm_check_nested_events().
Fixes: c300ab9f08 ("KVM: x86: Replace late check_nested_events() hack with more precise fix")
Cc: stable@vger.kernel.org
Reviewed-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
The kvm_x86_sync_pir_to_irr callback can sometimes set KVM_REQ_EVENT.
If that happens exactly at the time that an exit is handled as
EXIT_FASTPATH_REENTER_GUEST, vcpu_enter_guest will go incorrectly
through the loop that calls kvm_x86_run, instead of processing
the request promptly.
Fixes: 379a3c8ee4 ("KVM: VMX: Optimize posted-interrupt delivery for timer fastpath")
Cc: stable@vger.kernel.org
Reviewed-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Pull kvm fixes from Paolo Bonzini:
"Tools:
- kvm_stat: do not show halt_wait_ns since it is not a cumulative statistic
x86:
- clean ups and fixes for bus lock vmexit and lazy allocation of rmaps
- two fixes for SEV-ES (one more coming as soon as I get reviews)
- fix for static_key underflow
ARM:
- Properly refcount pages used as a concatenated stage-2 PGD
- Fix missing unlock when detecting the use of MTE+VM_SHARED"
* tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm:
KVM: SEV-ES: reduce ghcb_sa_len to 32 bits
KVM: VMX: Remove redundant handling of bus lock vmexit
KVM: kvm_stat: do not show halt_wait_ns
KVM: x86: WARN if APIC HW/SW disable static keys are non-zero on unload
Revert "KVM: x86: Open code necessary bits of kvm_lapic_set_base() at vCPU RESET"
KVM: SEV-ES: Set guest_state_protected after VMSA update
KVM: X86: fix lazy allocation of rmaps
KVM: SEV-ES: fix length of string I/O
KVM: arm64: Release mmap_lock when using VM_SHARED with MTE
KVM: arm64: Report corrupted refcount at EL2
KVM: arm64: Fix host stage-2 PGD refcount
KVM: s390: Function documentation fixes
Copying a user space buffer to the memory buffer is already available in
the FPU core. The copy mechanism in KVM lacks sanity checks and needs to
use cpuid() to lookup the offset of each component, while the FPU core has
this information cached.
Make the FPU core variant accessible for KVM and replace the home brewed
mechanism.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: kvm@vger.kernel.org
Link: https://lkml.kernel.org/r/20211015011539.134065207@linutronix.de
To date, VMM-directed TSC synchronization and migration has been a bit
messy. KVM has some baked-in heuristics around TSC writes to infer if
the VMM is attempting to synchronize. This is problematic, as it depends
on host userspace writing to the guest's TSC within 1 second of the last
write.
A much cleaner approach to configuring the guest's views of the TSC is to
simply migrate the TSC offset for every vCPU. Offsets are idempotent,
and thus not subject to change depending on when the VMM actually
reads/writes values from/to KVM. The VMM can then read the TSC once with
KVM_GET_CLOCK to capture a (realtime, host_tsc) pair at the instant when
the guest is paused.
Cc: David Matlack <dmatlack@google.com>
Cc: Sean Christopherson <seanjc@google.com>
Signed-off-by: Oliver Upton <oupton@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <20210916181538.968978-8-oupton@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Refactor kvm_synchronize_tsc to make a new function that allows callers
to specify TSC parameters (offset, value, nanoseconds, etc.) explicitly
for the sake of participating in TSC synchronization.
Signed-off-by: Oliver Upton <oupton@google.com>
Message-Id: <20210916181538.968978-7-oupton@google.com>
[Make sure kvm->arch.cur_tsc_generation and vcpu->arch.this_tsc_generation are
equal at the end of __kvm_synchronize_tsc, if matched is false. Reported by
Maxim Levitsky. - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Protect the reference point for kvmclock with a seqcount, so that
kvmclock updates for all vCPUs can proceed in parallel. Xen runstate
updates will also run in parallel and not bounce the kvmclock cacheline.
Of the variables that were protected by pvclock_gtod_sync_lock,
nr_vcpus_matched_tsc is different because it is updated outside
pvclock_update_vm_gtod_copy and read inside it. Therefore, we
need to keep it protected by a spinlock. In fact it must now
be a raw spinlock, because pvclock_update_vm_gtod_copy, being the
write-side of a seqcount, is non-preemptible. Since we already
have tsc_write_lock which is a raw spinlock, we can just use
tsc_write_lock as the lock that protects the write-side of the
seqcount.
Co-developed-by: Oliver Upton <oupton@google.com>
Message-Id: <20210916181538.968978-6-oupton@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Handling the migration of TSCs correctly is difficult, in part because
Linux does not provide userspace with the ability to retrieve a (TSC,
realtime) clock pair for a single instant in time. In lieu of a more
convenient facility, KVM can report similar information in the kvm_clock
structure.
Provide userspace with a host TSC & realtime pair iff the realtime clock
is based on the TSC. If userspace provides KVM_SET_CLOCK with a valid
realtime value, advance the KVM clock by the amount of elapsed time. Do
not step the KVM clock backwards, though, as it is a monotonic
oscillator.
Suggested-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Oliver Upton <oupton@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <20210916181538.968978-5-oupton@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This is a new warning in clang top-of-tree (will be clang 14):
In file included from arch/x86/kvm/mmu/mmu.c:27:
arch/x86/kvm/mmu/spte.h:318:9: error: use of bitwise '|' with boolean operands [-Werror,-Wbitwise-instead-of-logical]
return __is_bad_mt_xwr(rsvd_check, spte) |
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
||
arch/x86/kvm/mmu/spte.h:318:9: note: cast one or both operands to int to silence this warning
The code is fine, but change it anyway to shut up this clever clogs
of a compiler.
Reported-by: torvic9@mailbox.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
The size of the GHCB scratch area is limited to 16 KiB (GHCB_SCRATCH_AREA_LIMIT),
so there is no need for it to be a u64. This fixes a build error on 32-bit
systems:
i686-linux-gnu-ld: arch/x86/kvm/svm/sev.o: in function `sev_es_string_io:
sev.c:(.text+0x110f): undefined reference to `__udivdi3'
Cc: stable@vger.kernel.org
Fixes: 019057bd73 ("KVM: SEV-ES: fix length of string I/O")
Reported-by: Naresh Kamboju <naresh.kamboju@linaro.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Hardware may or may not set exit_reason.bus_lock_detected on BUS_LOCK
VM-Exits. Dealing with KVM_RUN_X86_BUS_LOCK in handle_bus_lock_vmexit
could be redundant when exit_reason.basic is EXIT_REASON_BUS_LOCK.
We can remove redundant handling of bus lock vmexit. Unconditionally Set
exit_reason.bus_lock_detected in handle_bus_lock_vmexit(), and deal with
KVM_RUN_X86_BUS_LOCK only in vmx_handle_exit().
Signed-off-by: Hao Xiang <hao.xiang@linux.alibaba.com>
Message-Id: <1634299161-30101-1-git-send-email-hao.xiang@linux.alibaba.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
WARN if the static keys used to track if any vCPU has disabled its APIC
are left elevated at module exit. Unlike the underflow case, nothing in
the static key infrastructure will complain if a key is left elevated,
and because an elevated key only affects performance, nothing in KVM will
fail if either key is improperly incremented.
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20211013003554.47705-3-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Revert a change to open code bits of kvm_lapic_set_base() when emulating
APIC RESET to fix an apic_hw_disabled underflow bug due to arch.apic_base
and apic_hw_disabled being unsyncrhonized when the APIC is created. If
kvm_arch_vcpu_create() fails after creating the APIC, kvm_free_lapic()
will see the initialized-to-zero vcpu->arch.apic_base and decrement
apic_hw_disabled without KVM ever having incremented apic_hw_disabled.
Using kvm_lapic_set_base() in kvm_lapic_reset() is also desirable for a
potential future where KVM supports RESET outside of vCPU creation, in
which case all the side effects of kvm_lapic_set_base() are needed, e.g.
to handle the transition from x2APIC => xAPIC.
Alternatively, KVM could temporarily increment apic_hw_disabled (and call
kvm_lapic_set_base() at RESET), but that's a waste of cycles and would
impact the performance of other vCPUs and VMs. The other subtle side
effect is that updating the xAPIC ID needs to be done at RESET regardless
of whether the APIC was previously enabled, i.e. kvm_lapic_reset() needs
an explicit call to kvm_apic_set_xapic_id() regardless of whether or not
kvm_lapic_set_base() also performs the update. That makes stuffing the
enable bit at vCPU creation slightly more palatable, as doing so affects
only the apic_hw_disabled key.
Opportunistically tweak the comment to explicitly call out the connection
between vcpu->arch.apic_base and apic_hw_disabled, and add a comment to
call out the need to always do kvm_apic_set_xapic_id() at RESET.
Underflow scenario:
kvm_vm_ioctl() {
kvm_vm_ioctl_create_vcpu() {
kvm_arch_vcpu_create() {
if (something_went_wrong)
goto fail_free_lapic;
/* vcpu->arch.apic_base is initialized when something_went_wrong is false. */
kvm_vcpu_reset() {
kvm_lapic_reset(struct kvm_vcpu *vcpu, bool init_event) {
vcpu->arch.apic_base = APIC_DEFAULT_PHYS_BASE | MSR_IA32_APICBASE_ENABLE;
}
}
return 0;
fail_free_lapic:
kvm_free_lapic() {
/* vcpu->arch.apic_base is not yet initialized when something_went_wrong is true. */
if (!(vcpu->arch.apic_base & MSR_IA32_APICBASE_ENABLE))
static_branch_slow_dec_deferred(&apic_hw_disabled); // <= underflow bug.
}
return r;
}
}
}
This (mostly) reverts commit 421221234a.
Fixes: 421221234a ("KVM: x86: Open code necessary bits of kvm_lapic_set_base() at vCPU RESET")
Reported-by: syzbot+9fc046ab2b0cf295a063@syzkaller.appspotmail.com
Debugged-by: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20211013003554.47705-2-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
If allocation of rmaps fails, but some of the pointers have already been written,
those pointers can be cleaned up when the memslot is freed, or even reused later
for another attempt at allocating the rmaps. Therefore there is no need to
WARN, as done for example in memslot_rmap_alloc, but the allocation *must* be
skipped lest KVM will overwrite the previous pointer and will indeed leak memory.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
The refactoring in commit bb18a67774 ("KVM: SEV: Acquire
vcpu mutex when updating VMSA") left behind the assignment to
svm->vcpu.arch.guest_state_protected; add it back.
Signed-off-by: Peter Gonda <pgonda@google.com>
[Delta between v2 and v3 of Peter's patch, which had already been
committed; the commit message is my own. - Paolo]
Fixes: bb18a67774 ("KVM: SEV: Acquire vcpu mutex when updating VMSA")
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
The size of the data in the scratch buffer is not divided by the size of
each port I/O operation, so vcpu->arch.pio.count ends up being larger
than it should be by a factor of size.
Cc: stable@vger.kernel.org
Fixes: 7ed9abfe8e ("KVM: SVM: Support string IO operations for an SEV-ES guest")
Acked-by: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Replace uses of sev_active() with the more generic cc_platform_has()
using CC_ATTR_GUEST_MEM_ENCRYPT. If future support is added for other
memory encryption technologies, the use of CC_ATTR_GUEST_MEM_ENCRYPT
can be updated, as required.
Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20210928191009.32551-7-bp@alien8.de
The recent change to make objtool aware of more symbol relocation types
(commit 24ff652573: "objtool: Teach get_alt_entry() about more
relocation types") also added another check, and resulted in this
objtool warning when building kvm on x86:
arch/x86/kvm/emulate.o: warning: objtool: __ex_table+0x4: don't know how to handle reloc symbol type: kvm_fastop_exception
The reason seems to be that kvm_fastop_exception() is marked as a global
symbol, which causes the relocation to ke kept around for objtool. And
at the same time, the kvm_fastop_exception definition (which is done as
an inline asm statement) doesn't actually set the type of the global,
which then makes objtool unhappy.
The minimal fix is to just not mark kvm_fastop_exception as being a
global symbol. It's only used in that one compilation unit anyway, so
it was always pointless. That's how all the other local exception table
labels are done.
I'm not entirely happy about the kinds of games that the kvm code plays
with doing its own exception handling, and the fact that it confused
objtool is most definitely a symptom of the code being a bit too subtle
and ad-hoc. But at least this trivial one-liner makes objtool no longer
upset about what is going on.
Fixes: 24ff652573 ("objtool: Teach get_alt_entry() about more relocation types")
Link: https://lore.kernel.org/lkml/CAHk-=wiZwq-0LknKhXN4M+T8jbxn_2i9mcKpO+OaBSSq_Eh7tg@mail.gmail.com/
Cc: Borislav Petkov <bp@suse.de>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Sean Christopherson <seanjc@google.com>
Cc: Vitaly Kuznetsov <vkuznets@redhat.com>
Cc: Wanpeng Li <wanpengli@tencent.com>
Cc: Jim Mattson <jmattson@google.com>
Cc: Joerg Roedel <joro@8bytes.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Avoid allocating the gfn_track arrays if nothing needs them. If there
are no external to KVM users of the API (i.e. no GVT-g), then page
tracking is only needed for shadow page tables. This means that when tdp
is enabled and there are no external users, then the gfn_track arrays
can be lazily allocated when the shadow MMU is actually used. This avoid
allocations equal to .05% of guest memory when nested virtualization is
not used, if the kernel is compiled without GVT-g.
Signed-off-by: David Stevens <stevensd@chromium.org>
Message-Id: <20210922045859.2011227-3-stevensd@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
According to section "TLB Flush" in APM vol 2,
"Support for TLB_CONTROL commands other than the first two, is
optional and is indicated by CPUID Fn8000_000A_EDX[FlushByAsid].
All encodings of TLB_CONTROL not defined in the APM are reserved."
Signed-off-by: Krish Sadhukhan <krish.sadhukhan@oracle.com>
Message-Id: <20210920235134.101970-3-krish.sadhukhan@oracle.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
By switching from kfree() to kvfree() in kvm_arch_free_vm() Arm64 can
use the common variant. This can be accomplished by adding another
macro __KVM_HAVE_ARCH_VM_FREE, which will be used only by x86 for now.
Further simplification can be achieved by adding __kvm_arch_free_vm()
doing the common part.
Suggested-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
Message-Id: <20210903130808.30142-5-jgross@suse.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Predictive Store Forwarding: AMD Zen3 processors feature a new
technology called Predictive Store Forwarding (PSF).
PSF is a hardware-based micro-architectural optimization designed
to improve the performance of code execution by predicting address
dependencies between loads and stores.
How PSF works:
It is very common for a CPU to execute a load instruction to an address
that was recently written by a store. Modern CPUs implement a technique
known as Store-To-Load-Forwarding (STLF) to improve performance in such
cases. With STLF, data from the store is forwarded directly to the load
without having to wait for it to be written to memory. In a typical CPU,
STLF occurs after the address of both the load and store are calculated
and determined to match.
PSF expands on this by speculating on the relationship between loads and
stores without waiting for the address calculation to complete. With PSF,
the CPU learns over time the relationship between loads and stores. If
STLF typically occurs between a particular store and load, the CPU will
remember this.
In typical code, PSF provides a performance benefit by speculating on
the load result and allowing later instructions to begin execution
sooner than they otherwise would be able to.
The details of security analysis of AMD predictive store forwarding is
documented here.
https://www.amd.com/system/files/documents/security-analysis-predictive-store-forwarding.pdf
Predictive Store Forwarding controls:
There are two hardware control bits which influence the PSF feature:
- MSR 48h bit 2 – Speculative Store Bypass (SSBD)
- MSR 48h bit 7 – Predictive Store Forwarding Disable (PSFD)
The PSF feature is disabled if either of these bits are set. These bits
are controllable on a per-thread basis in an SMT system. By default, both
SSBD and PSFD are 0 meaning that the speculation features are enabled.
While the SSBD bit disables PSF and speculative store bypass, PSFD only
disables PSF.
PSFD may be desirable for software which is concerned with the
speculative behavior of PSF but desires a smaller performance impact than
setting SSBD.
Support for PSFD is indicated in CPUID Fn8000_0008 EBX[28].
All processors that support PSF will also support PSFD.
Linux kernel does not have the interface to enable/disable PSFD yet. Plan
here is to expose the PSFD technology to KVM so that the guest kernel can
make use of it if they wish to.
Signed-off-by: Babu Moger <Babu.Moger@amd.com>
Message-Id: <163244601049.30292.5855870305350227855.stgit@bmoger-ubuntu>
[Keep feature private to KVM, as requested by Borislav Petkov. - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
mmu_try_to_unsync_pages checks if page tracking is active for the given
gfn, which requires knowing the memslot. We can pass down the memslot
via make_spte to avoid this lookup.
The memslot is also handy for make_spte's marking of the gfn as dirty:
we can test whether dirty page tracking is enabled, and if so ensure that
pages are mapped as writable with 4K granularity. Apart from the warning,
no functional change is intended.
Signed-off-by: David Matlack <dmatlack@google.com>
Message-Id: <20210813203504.2742757-7-dmatlack@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
mmu_set_spte is called for either PTE prefetching or page faults. The
three boolean arguments write_fault, speculative and host_writable are
always respectively false/true/true for prefetching and coming from
a struct kvm_page_fault for page faults.
Let mmu_set_spte distinguish these two situation by accepting a
possibly NULL struct kvm_page_fault argument.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
The level and A/D bit support of the new SPTE can be found in the role,
which is stored in the kvm_mmu_page struct. This merges two arguments
into one.
For the TDP MMU, the kvm_mmu_page was not used (kvm_tdp_mmu_map does
not use it if the SPTE is already present) so we fetch it just before
calling make_spte.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Prepare for removing the ad_disabled argument of make_spte; instead it can
be found in the role of a struct kvm_mmu_page. First of all, the TDP MMU
must set the role accurately.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
The level of the new SPTE can be found in the kvm_mmu_page struct; there
is no need to pass it down.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Now that make_spte is called directly by the shadow MMU (rather than
wrapped by set_spte), it only has to return one boolean value.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Since the two callers of set_spte do different things with the results,
inlining it actually makes the code simpler to reason about. For example,
FNAME(sync_page) already has a struct kvm_mmu_page *, but set_spte had to
fish it back out of sptep's private page data.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Since the two callers of set_spte do different things with the results,
inlining it actually makes the code simpler to reason about. For example,
mmu_set_spte looks quite like tdp_mmu_map_handle_target_level, but the
similarity is hidden by set_spte.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
The memslot for the faulting gfn is used throughout the page fault
handling code, so capture it in kvm_page_fault as soon as we know the
gfn and use it in the page fault handling code that has direct access
to the kvm_page_fault struct. Replace various tests using is_noslot_pfn
with more direct tests on fault->slot being NULL.
This, in combination with the subsequent patch, improves "Populate
memory time" in dirty_log_perf_test by 5% when using the legacy MMU.
There is no discerable improvement to the performance of the TDP MMU.
No functional change intended.
Suggested-by: Ben Gardon <bgardon@google.com>
Signed-off-by: David Matlack <dmatlack@google.com>
Message-Id: <20210813203504.2742757-4-dmatlack@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
tdp_mmu_map_set_spte_atomic is not taking care of dirty logging anymore,
the only difference that remains is that it takes a vCPU instead of
the struct kvm. Merge the two functions.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
