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[91.219.240.2]) by smtp.gmail.com with ESMTPSA id cc9sm5811982edb.14.2020.07.30.04.16.10 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 30 Jul 2020 04:16:10 -0700 (PDT) From: Vitaly Kuznetsov To: Wanpeng Li Cc: LKML , kvm , Paolo Bonzini , Sean Christopherson , Wanpeng Li , Jim Mattson , Joerg Roedel Subject: Re: [PATCH v2 3/3] KVM: SVM: Fix disable pause loop exit/pause filtering capability on SVM In-Reply-To: References: <1595929506-9203-1-git-send-email-wanpengli@tencent.com> <1595929506-9203-3-git-send-email-wanpengli@tencent.com> <87k0ymldg9.fsf@vitty.brq.redhat.com> Date: Thu, 30 Jul 2020 13:16:09 +0200 Message-ID: <875za5l0cm.fsf@vitty.brq.redhat.com> MIME-Version: 1.0 Content-Type: text/plain Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org Wanpeng Li writes: > On Wed, 29 Jul 2020 at 20:21, Vitaly Kuznetsov wrote: >> >> Wanpeng Li writes: >> >> > From: Wanpeng Li >> > >> > 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 >> > Tested-by: Haiwei Li >> > Fixes: 8566ac8b (KVM: SVM: Implement pause loop exit logic in SVM) >> > Signed-off-by: Wanpeng Li >> > --- >> > 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