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| author | Lai Jiangshan <laijs@linux.alibaba.com> | 2021-06-01 01:46:28 +0800 |
|---|---|---|
| committer | Paolo Bonzini <pbonzini@redhat.com> | 2021-06-08 13:15:20 -0400 |
| commit | af3511ff7fa2107d6410831f3d71030f5e8d2b25 (patch) | |
| tree | 2f97e39acd2001b3c473b61754b52cf8af63d553 /arch | |
| parent | b1bd5cba3306691c771d558e94baa73e8b0b96b7 (diff) | |
| download | lwn-af3511ff7fa2107d6410831f3d71030f5e8d2b25.tar.gz lwn-af3511ff7fa2107d6410831f3d71030f5e8d2b25.zip | |
KVM: x86: Ensure PV TLB flush tracepoint reflects KVM behavior
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@linux.alibaba.com>
Message-Id: <20210531174628.10265-1-jiangshanlai@gmail.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/x86/kvm/x86.c | 6 |
1 files changed, 4 insertions, 2 deletions
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 1cd6d4685932..e2144eedaf79 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -3101,9 +3101,11 @@ static void record_steal_time(struct kvm_vcpu *vcpu) * 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; |