From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1173308AbdDXQQc (ORCPT ); Mon, 24 Apr 2017 12:16:32 -0400 Received: from mail-bn3nam01on0067.outbound.protection.outlook.com ([104.47.33.67]:44312 "EHLO NAM01-BN3-obe.outbound.protection.outlook.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S973309AbdDXQQN (ORCPT ); Mon, 24 Apr 2017 12:16:13 -0400 Authentication-Results: amd.com; dkim=none (message not signed) header.d=none;amd.com; dmarc=none action=none header.from=amd.com; Subject: Re: [PATCH] x86: kvm: Avoid guest page table walk when gpa_available is set To: , , , , References: <1493049146-19261-1-git-send-email-brijesh.singh@amd.com> CC: , , , , , From: Brijesh Singh Message-ID: <407864ef-c815-6e94-a8c3-0307821d513a@amd.com> Date: Mon, 24 Apr 2017 11:16:05 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.8.0 MIME-Version: 1.0 In-Reply-To: <1493049146-19261-1-git-send-email-brijesh.singh@amd.com> Content-Type: text/plain; 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Lets not limit > the gpa_available optimization to just MMIO region. The patch extends > the check to avoid page walk whenever gpa_available flag is set. > > Signed-off-by: Brijesh Singh > --- > arch/x86/include/asm/kvm_host.h | 1 + > arch/x86/kvm/svm.c | 4 ++++ > arch/x86/kvm/x86.c | 26 +++++++++++++++----------- > 3 files changed, 20 insertions(+), 11 deletions(-) > > diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h > index 74ef58c..491326d 100644 > --- a/arch/x86/include/asm/kvm_host.h > +++ b/arch/x86/include/asm/kvm_host.h > @@ -677,6 +677,7 @@ struct kvm_vcpu_arch { > > /* GPA available (AMD only) */ > bool gpa_available; > + gpa_t gpa_val; > }; > > struct kvm_lpage_info { > diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c > index 5fba706..8827e4b 100644 > --- a/arch/x86/kvm/svm.c > +++ b/arch/x86/kvm/svm.c > @@ -4159,6 +4159,10 @@ static int handle_exit(struct kvm_vcpu *vcpu) > > vcpu->arch.gpa_available = (exit_code == SVM_EXIT_NPF); > > + /* On #NPF, exit_info_2 contain a valid GPA */ > + if (vcpu->arch.gpa_available) > + vcpu->arch.gpa_val = svm->vmcb->control.exit_info_2; > + > if (!is_cr_intercept(svm, INTERCEPT_CR0_WRITE)) > vcpu->arch.cr0 = svm->vmcb->save.cr0; > if (npt_enabled) > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > index ccbd45e..18ec746 100644 > --- a/arch/x86/kvm/x86.c > +++ b/arch/x86/kvm/x86.c > @@ -4653,18 +4653,16 @@ static int emulator_read_write_onepage(unsigned long addr, void *val, > * occurred. > */ > if (vcpu->arch.gpa_available && > - emulator_can_use_gpa(ctxt) && > - vcpu_is_mmio_gpa(vcpu, addr, exception->address, write) && > - (addr & ~PAGE_MASK) == (exception->address & ~PAGE_MASK)) { > + emulator_can_use_gpa(ctxt) && > + (addr & ~PAGE_MASK) == (exception->address & ~PAGE_MASK)) { > gpa = exception->address; > - goto mmio; > + ret = vcpu_is_mmio_gpa(vcpu, addr, gpa, write); > + } else { > + ret = vcpu_mmio_gva_to_gpa(vcpu, addr, &gpa, exception, write); > + if (ret < 0) > + return X86EMUL_PROPAGATE_FAULT; > } > > - ret = vcpu_mmio_gva_to_gpa(vcpu, addr, &gpa, exception, write); > - > - if (ret < 0) > - return X86EMUL_PROPAGATE_FAULT; > - > /* For APIC access vmexit */ > if (ret) > goto mmio; > @@ -5675,8 +5673,14 @@ int x86_emulate_instruction(struct kvm_vcpu *vcpu, > } > > restart: > - /* Save the faulting GPA (cr2) in the address field */ > - ctxt->exception.address = cr2; > + /* > + * Save the faulting GPA (cr2) in the address field > + * NOTE: If gpa_available is set then gpa_val will contain a valid GPA > + */ > + if (vcpu->arch.gpa_available) > + ctxt->exception.address = vcpu->arch.gpa_val; > + else > + ctxt->exception.address = cr2; > > r = x86_emulate_insn(ctxt); > >