From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751961AbdK2GIB (ORCPT ); Wed, 29 Nov 2017 01:08:01 -0500 Received: from mail-pf0-f194.google.com ([209.85.192.194]:33909 "EHLO mail-pf0-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751054AbdK2GH7 (ORCPT ); Wed, 29 Nov 2017 01:07:59 -0500 X-Google-Smtp-Source: AGs4zMYTIMOQ2pU0QIufDJ2NuR3YSl5MyvNfp8Mk5U6yeYjAUdFzkOiG8hXAFld5yW/kd2AmkWgM3w== From: Wanpeng Li X-Google-Original-From: Wanpeng Li To: linux-kernel@vger.kernel.org, kvm@vger.kernel.org Cc: Paolo Bonzini , =?UTF-8?q?Radim=20Kr=C4=8Dm=C3=A1=C5=99?= , Wanpeng Li , Jim Mattson Subject: [PATCH] KVM: VMX: Cache IA32_DEBUGCTL in memory Date: Tue, 28 Nov 2017 22:07:53 -0800 Message-Id: <1511935673-7371-1-git-send-email-wanpeng.li@hotmail.com> X-Mailer: git-send-email 2.7.4 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Wanpeng Li MSR_IA32_DEBUGCTLMSR is zeroed on VMEXIT, so it is saved/restored each time during world switch. Jim from Google pointed out that when running schbench in L2, vmx_vcpu_run will occupy 4% cpu time, and the 25% of vmx_vcpu_run cpu time is occupied by get_debugctlmsr(). This patch caches the host IA32_DEBUGCTL MSR and saves/restores the host IA32_DEBUGCTL msr when guest/host switches to avoid to save/restore each time during world switch. Suggested-by: Jim Mattson Cc: Jim Mattson Cc: Paolo Bonzini Cc: Radim Krčmář Signed-off-by: Wanpeng Li --- arch/x86/include/asm/kvm_host.h | 1 + arch/x86/kvm/vmx.c | 11 +++++------ 2 files changed, 6 insertions(+), 6 deletions(-) diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h index 63d34bc..c904250 100644 --- a/arch/x86/include/asm/kvm_host.h +++ b/arch/x86/include/asm/kvm_host.h @@ -619,6 +619,7 @@ struct kvm_vcpu_arch { unsigned long dr7; unsigned long eff_db[KVM_NR_DB_REGS]; unsigned long guest_debug_dr7; + unsigned long debugctlmsr; u64 msr_platform_info; u64 msr_misc_features_enables; diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c index 8c7e816..b167bba 100644 --- a/arch/x86/kvm/vmx.c +++ b/arch/x86/kvm/vmx.c @@ -2326,6 +2326,7 @@ static void vmx_vcpu_load(struct kvm_vcpu *vcpu, int cpu) vmx_vcpu_pi_load(vcpu, cpu); vmx->host_pkru = read_pkru(); + vcpu->arch.debugctlmsr = get_debugctlmsr(); } static void vmx_vcpu_pi_put(struct kvm_vcpu *vcpu) @@ -2347,6 +2348,9 @@ static void vmx_vcpu_put(struct kvm_vcpu *vcpu) vmx_vcpu_pi_put(vcpu); __vmx_load_host_state(to_vmx(vcpu)); + /* MSR_IA32_DEBUGCTLMSR is zeroed on vmexit. Restore it if needed */ + if (vcpu->arch.debugctlmsr) + update_debugctlmsr(vcpu->arch.debugctlmsr); } static bool emulation_required(struct kvm_vcpu *vcpu) @@ -9346,7 +9350,7 @@ static void vmx_arm_hv_timer(struct kvm_vcpu *vcpu) static void __noclone vmx_vcpu_run(struct kvm_vcpu *vcpu) { struct vcpu_vmx *vmx = to_vmx(vcpu); - unsigned long debugctlmsr, cr3, cr4; + unsigned long cr3, cr4; /* Record the guest's net vcpu time for enforced NMI injections. */ if (unlikely(!enable_vnmi && @@ -9399,7 +9403,6 @@ static void __noclone vmx_vcpu_run(struct kvm_vcpu *vcpu) __write_pkru(vcpu->arch.pkru); atomic_switch_perf_msrs(vmx); - debugctlmsr = get_debugctlmsr(); vmx_arm_hv_timer(vcpu); @@ -9509,10 +9512,6 @@ static void __noclone vmx_vcpu_run(struct kvm_vcpu *vcpu) #endif ); - /* MSR_IA32_DEBUGCTLMSR is zeroed on vmexit. Restore it if needed */ - if (debugctlmsr) - update_debugctlmsr(debugctlmsr); - #ifndef CONFIG_X86_64 /* * The sysexit path does not restore ds/es, so we must set them to -- 2.7.4