On Sat, May 08, 2021, Wanpeng Li wrote: > From: Wanpeng Li <wanpengli@xxxxxxxxxxx> > > 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 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) > Cc: stable@xxxxxxxxxxxxxxx > Signed-off-by: Wanpeng Li <wanpengli@xxxxxxxxxxx> > --- > arch/x86/kvm/x86.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > index c0244a6..c38e990 100644 > --- a/arch/x86/kvm/x86.c > +++ b/arch/x86/kvm/x86.c > @@ -3105,7 +3105,8 @@ static void record_steal_time(struct kvm_vcpu *vcpu) > 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; Curly braces needed since the if-statment needs 'em. Other than that, Reviewed-by: Sean Christopherson <seanjc@xxxxxxxxxx> > > vcpu->arch.st.preempted = 0; > > -- > 2.7.4 >
