From: Wanpeng Li <kernellwp@gmail.com> To: Sean Christopherson <seanjc@google.com> Cc: LKML <linux-kernel@vger.kernel.org>, kvm <kvm@vger.kernel.org>, Paolo Bonzini <pbonzini@redhat.com>, Vitaly Kuznetsov <vkuznets@redhat.com>, Wanpeng Li <wanpengli@tencent.com>, Jim Mattson <jmattson@google.com>, Joerg Roedel <joro@8bytes.org>, "# v3 . 10+" <stable@vger.kernel.org> Subject: Re: [PATCH 3/3] KVM: X86: Fix vCPU preempted state from guest point of view Date: Tue, 11 May 2021 18:28:51 +0800 [thread overview] Message-ID: <CANRm+Cy55bgvETx2gdVEFnaciEvi=1p-uUWojZdsn2_2X1AWUQ@mail.gmail.com> (raw) In-Reply-To: <YJnNPpalqYwERwEL@google.com> On Tue, 11 May 2021 at 08:18, Sean Christopherson <seanjc@google.com> wrote: > > On Sat, May 08, 2021, Wanpeng Li wrote: > > From: Wanpeng Li <wanpengli@tencent.com> > > > > 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@vger.kernel.org > > Signed-off-by: Wanpeng Li <wanpengli@tencent.com> > > --- > > 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@google.com> > > > > > vcpu->arch.st.preempted = 0; > > > > -- > > 2.7.4 > >
next prev parent reply other threads:[~2021-05-11 10:29 UTC|newest] Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top 2021-05-08 9:31 [PATCH 1/3] KVM: PPC: Book3S HV: exit halt polling on need_resched() as well Wanpeng Li 2021-05-08 9:31 ` [PATCH 2/3] KVM: X86: Bail out of direct yield in case of undercomitted scenarios Wanpeng Li 2021-05-11 21:44 ` Sean Christopherson 2021-05-12 2:43 ` Wanpeng Li 2021-05-12 16:59 ` Sean Christopherson 2021-05-08 9:31 ` [PATCH 3/3] KVM: X86: Fix vCPU preempted state from guest point of view Wanpeng Li 2021-05-11 0:18 ` Sean Christopherson 2021-05-11 10:28 ` Wanpeng Li [this message] 2021-05-12 0:02 ` [PATCH 1/3] KVM: PPC: Book3S HV: exit halt polling on need_resched() as well Wanpeng Li
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