From: Wanpeng Li <kernellwp@gmail.com>
To: Vitaly Kuznetsov <vkuznets@redhat.com>
Cc: LKML <linux-kernel@vger.kernel.org>, kvm <kvm@vger.kernel.org>,
Paolo Bonzini <pbonzini@redhat.com>,
Sean Christopherson <sean.j.christopherson@intel.com>,
Wanpeng Li <wanpengli@tencent.com>,
Jim Mattson <jmattson@google.com>, Joerg Roedel <joro@8bytes.org>
Subject: Re: [PATCH v2 3/3] KVM: SVM: Fix disable pause loop exit/pause filtering capability on SVM
Date: Thu, 30 Jul 2020 08:56:42 +0800 [thread overview]
Message-ID: <CANRm+Cx-VM=QGcDNG0oRq7YX+2wmmw8yDjESrJGxTeEWkUUv0A@mail.gmail.com> (raw)
In-Reply-To: <87k0ymldg9.fsf@vitty.brq.redhat.com>
On Wed, 29 Jul 2020 at 20:21, Vitaly Kuznetsov <vkuznets@redhat.com> wrote:
>
> Wanpeng Li <kernellwp@gmail.com> writes:
>
> > From: Wanpeng Li <wanpengli@tencent.com>
> >
> > Commit 8566ac8b (KVM: SVM: Implement pause loop exit logic in SVM) drops
> > disable pause loop exit/pause filtering capability completely, I guess it
> > is a merge fault by Radim since disable vmexits capabilities and pause
> > loop exit for SVM patchsets are merged at the same time. This patch
> > reintroduces the disable pause loop exit/pause filtering capability
> > support.
> >
> > We can observe 2.9% hackbench improvement for a 92 vCPUs guest on AMD
> > Rome Server.
> >
> > Reported-by: Haiwei Li <lihaiwei@tencent.com>
> > Tested-by: Haiwei Li <lihaiwei@tencent.com>
> > Fixes: 8566ac8b (KVM: SVM: Implement pause loop exit logic in SVM)
> > Signed-off-by: Wanpeng Li <wanpengli@tencent.com>
> > ---
> > arch/x86/kvm/svm/svm.c | 9 ++++++---
> > 1 file changed, 6 insertions(+), 3 deletions(-)
> >
> > diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
> > index c0da4dd..c20f127 100644
> > --- a/arch/x86/kvm/svm/svm.c
> > +++ b/arch/x86/kvm/svm/svm.c
> > @@ -1090,7 +1090,7 @@ static void init_vmcb(struct vcpu_svm *svm)
> > svm->nested.vmcb = 0;
> > svm->vcpu.arch.hflags = 0;
> >
> > - if (pause_filter_count) {
> > + if (pause_filter_count && !kvm_pause_in_guest(svm->vcpu.kvm)) {
> > control->pause_filter_count = pause_filter_count;
> > if (pause_filter_thresh)
> > control->pause_filter_thresh = pause_filter_thresh;
> > @@ -2693,7 +2693,7 @@ static int pause_interception(struct vcpu_svm *svm)
> > struct kvm_vcpu *vcpu = &svm->vcpu;
> > bool in_kernel = (svm_get_cpl(vcpu) == 0);
> >
> > - if (pause_filter_thresh)
> > + if (!kvm_pause_in_guest(vcpu->kvm))
> > grow_ple_window(vcpu);
> >
> > kvm_vcpu_on_spin(vcpu, in_kernel);
> > @@ -3780,7 +3780,7 @@ static void svm_handle_exit_irqoff(struct kvm_vcpu *vcpu)
> >
> > static void svm_sched_in(struct kvm_vcpu *vcpu, int cpu)
> > {
> > - if (pause_filter_thresh)
> > + if (!kvm_pause_in_guest(vcpu->kvm))
> > shrink_ple_window(vcpu);
> > }
> >
> > @@ -3958,6 +3958,9 @@ static void svm_vm_destroy(struct kvm *kvm)
> >
> > static int svm_vm_init(struct kvm *kvm)
> > {
> > + if (!pause_filter_thresh)
> > + kvm->arch.pause_in_guest = true;
>
> Would it make sense to do
>
> if (!pause_filter_count || !pause_filter_thresh)
> kvm->arch.pause_in_guest = true;
>
> here and simplify the condition in init_vmcb()?
kvm->arch.pause_in_guest can also be true when userspace sets the
KVM_CAP_X86_DISABLE_EXITS capability, so we can't simplify the
condition in init_vmcb().
Wanpeng
next prev parent reply other threads:[~2020-07-30 0:57 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-28 9:45 [PATCH v2 1/3] KVM: LAPIC: Prevent setting the tscdeadline timer if the lapic is hw disabled Wanpeng Li
2020-07-28 9:45 ` [PATCH v2 2/3] KVM: LAPIC: Set the APIC_TDCR settable bits Wanpeng Li
2020-07-28 9:45 ` [PATCH v2 3/3] KVM: SVM: Fix disable pause loop exit/pause filtering capability on SVM Wanpeng Li
2020-07-29 12:20 ` Vitaly Kuznetsov
2020-07-30 0:56 ` Wanpeng Li [this message]
2020-07-30 11:16 ` Vitaly Kuznetsov
2020-07-31 3:18 ` Wanpeng Li
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