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 @@ -3015,6 +3015,8 @@ 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;