20210531174628.10265-1-jiangshanlai@xxxxxxxxx>
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This is a note to let you know that I've just added the patch titled
KVM: x86: Ensure PV TLB flush tracepoint reflects KVM behavior
to the 5.10-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
kvm-x86-ensure-pv-tlb-flush-tracepoint-reflects-kvm-behavior.patch
and it can be found in the queue-5.10 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From stable-owner@xxxxxxxxxxxxxxx Wed May 10 20:16:27 2023
From: Rishabh Bhatnagar <risbhat@xxxxxxxxxx>
Date: Wed, 10 May 2023 18:15:39 +0000
Subject: KVM: x86: Ensure PV TLB flush tracepoint reflects KVM behavior
To: <gregkh@xxxxxxxxxxxxxxxxxxx>, <stable@xxxxxxxxxxxxxxx>
Cc: <lee@xxxxxxxxxx>, <seanjc@xxxxxxxxxx>, <kvm@xxxxxxxxxxxxxxx>, <bp@xxxxxxxxx>, <mingo@xxxxxxxxxx>, <tglx@xxxxxxxxxxxxx>, <pbonzini@xxxxxxxxxx>, <vkuznets@xxxxxxxxxx>, <wanpengli@xxxxxxxxxxx>, <jmattson@xxxxxxxxxx>, <joro@xxxxxxxxxx>, Lai Jiangshan <laijs@xxxxxxxxxxxxxxxxx>, Rishabh Bhatnagar <risbhat@xxxxxxxxxx>, Allen Pais <apais@xxxxxxxxxxxxxxxxxxx>
Message-ID: <20230510181547.22451-2-risbhat@xxxxxxxxxx>
From: Rishabh Bhatnagar <risbhat@xxxxxxxxxx>
From: Lai Jiangshan <laijs@xxxxxxxxxxxxxxxxx>
commit af3511ff7fa2107d6410831f3d71030f5e8d2b25 upstream.
In record_steal_time(), st->preempted is read twice, and
trace_kvm_pv_tlb_flush() might output result inconsistent if
kvm_vcpu_flush_tlb_guest() see a different st->preempted later.
It is a very trivial problem and hardly has actual harm and can be
avoided by reseting and reading st->preempted in atomic way via xchg().
Signed-off-by: Lai Jiangshan <laijs@xxxxxxxxxxxxxxxxx>
Message-Id: <20210531174628.10265-1-jiangshanlai@xxxxxxxxx>
Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Signed-off-by: Rishabh Bhatnagar <risbhat@xxxxxxxxxx>
Tested-by: Allen Pais <apais@xxxxxxxxxxxxxxxxxxx>
Acked-by: Sean Christopherson <seanjc@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/x86/kvm/x86.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -3041,9 +3041,11 @@ static void record_steal_time(struct kvm
* expensive IPIs.
*/
if (guest_pv_has(vcpu, KVM_FEATURE_PV_TLB_FLUSH)) {
+ u8 st_preempted = xchg(&st->preempted, 0);
+
trace_kvm_pv_tlb_flush(vcpu->vcpu_id,
- st->preempted & KVM_VCPU_FLUSH_TLB);
- if (xchg(&st->preempted, 0) & KVM_VCPU_FLUSH_TLB)
+ st_preempted & KVM_VCPU_FLUSH_TLB);
+ if (st_preempted & KVM_VCPU_FLUSH_TLB)
kvm_vcpu_flush_tlb_guest(vcpu);
} else {
st->preempted = 0;
Patches currently in stable-queue which might be from stable-owner@xxxxxxxxxxxxxxx are
queue-5.10/kvm-fix-steal-time-asm-constraints.patch
queue-5.10/kvm-x86-ensure-pv-tlb-flush-tracepoint-reflects-kvm-behavior.patch
queue-5.10/blk-crypto-make-blk_crypto_evict_key-more-robust.patch
queue-5.10/kvm-x86-do-not-report-preemption-if-the-steal-time-cache-is-stale.patch
queue-5.10/kvm-x86-do-not-set-st-preempted-when-going-back-to-user-space.patch
queue-5.10/kvm-x86-move-guest_pv_has-out-of-user_access-section.patch
queue-5.10/kvm-x86-fix-recording-of-guest-steal-time-preempted-status.patch
queue-5.10/blk-mq-release-crypto-keyslot-before-reporting-i-o-complete.patch
queue-5.10/kvm-x86-revalidate-steal-time-cache-if-msr-value-changes.patch
queue-5.10/blk-crypto-make-blk_crypto_evict_key-return-void.patch
queue-5.10/kvm-x86-remove-obsolete-disabling-of-page-faults-in-kvm_arch_vcpu_put.patch
