On Tue, 11 May 2021 at 08:18, Sean Christopherson <seanjc@xxxxxxxxxx> wrote: > > 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, Will send out a new version after 1-2 get reviewed. :) > > Reviewed-by: Sean Christopherson <seanjc@xxxxxxxxxx> > > > > > vcpu->arch.st.preempted = 0; > > > > -- > > 2.7.4 > >
