Messages in this thread Patch in this message | | | From | Greg Kroah-Hartman <> | Subject | [PATCH 5.10 057/252] KVM: X86: Fix vCPU preempted state from guests point of view | Date | Mon, 31 May 2021 15:12:02 +0200 |
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From: Wanpeng Li <wanpengli@tencent.com>
commit 1eff0ada88b48e4ac1e3fe26483b3684fedecd27 upstream.
Commit 66570e966dd9 (kvm: x86: only provide PV features if enabled in guest's CPUID) avoids to access pv tlb shootdown host side logic when this pv feature is not exposed to guest, however, kvm_steal_time.preempted not only leveraged by pv tlb shootdown logic but also mitigate the lock holder preemption issue. >From guest's point of view, vCPU is always preempted since we lose the reset of kvm_steal_time.preempted before vmentry if pv tlb shootdown feature is not exposed. This patch fixes it by clearing kvm_steal_time.preempted before vmentry.
Fixes: 66570e966dd9 (kvm: x86: only provide PV features if enabled in guest's CPUID) Reviewed-by: Sean Christopherson <seanjc@google.com> Cc: stable@vger.kernel.org Signed-off-by: Wanpeng Li <wanpengli@tencent.com> Message-Id: <1621339235-11131-3-git-send-email-wanpengli@tencent.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> --- arch/x86/kvm/x86.c | 2 ++ 1 file changed, 2 insertions(+)
--- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -3006,6 +3006,8 @@ static void record_steal_time(struct kvm st->preempted & KVM_VCPU_FLUSH_TLB); if (xchg(&st->preempted, 0) & KVM_VCPU_FLUSH_TLB) kvm_vcpu_flush_tlb_guest(vcpu); + } else { + st->preempted = 0; } vcpu->arch.st.preempted = 0;
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