From: Vitaly Kuznetsov <vkuznets@redhat.com>
To: Wanpeng Li <kernellwp@gmail.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 13:16:09 +0200 [thread overview]
Message-ID: <875za5l0cm.fsf@vitty.brq.redhat.com> (raw)
In-Reply-To: <CANRm+Cx-VM=QGcDNG0oRq7YX+2wmmw8yDjESrJGxTeEWkUUv0A@mail.gmail.com>
Wanpeng Li <kernellwp@gmail.com> writes:
> 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().
>
I meant we simplify it to
if (!kvm_pause_in_guest(svm->vcpu.kvm))
as "!pause_filter_count" gets included.
--
Vitaly
next prev parent reply other threads:[~2020-07-30 11:16 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
2020-07-30 11:16 ` Vitaly Kuznetsov [this message]
2020-07-31 3:18 ` Wanpeng Li
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