Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932112AbbFQMbh (ORCPT ); Wed, 17 Jun 2015 08:31:37 -0400 Received: from mx1.redhat.com ([209.132.183.28]:41051 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754697AbbFQMba (ORCPT ); Wed, 17 Jun 2015 08:31:30 -0400 Message-ID: <5581689D.6020002@redhat.com> Date: Wed, 17 Jun 2015 14:31:25 +0200 From: Paolo Bonzini User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.6.0 MIME-Version: 1.0 To: Bandan Das , kvm@vger.kernel.org CC: linux-kernel@vger.kernel.org, Radim Krcmar , jan.kiszka@siemens.com Subject: Re: [PATCH] KVM: nSVM: Check for NRIPS support before updating control field References: In-Reply-To: Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1848 Lines: 54 On 11/06/2015 08:05, Bandan Das wrote: > > If hardware doesn't support DecodeAssist - a feature that provides > more information about the intercept in the VMCB, KVM decodes the > instruction and then updates the next_rip vmcb control field. > However, NRIP support itself depends on cpuid Fn8000_000A_EDX[NRIPS]. > Since skip_emulated_instruction() doesn't verify nrip support > before accepting control.next_rip as valid, avoid writing this > field if support isn't present. > > Signed-off-by: Bandan Das > --- > arch/x86/kvm/svm.c | 8 ++++++-- > 1 file changed, 6 insertions(+), 2 deletions(-) > > diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c > index 9afa233..4911bf1 100644 > --- a/arch/x86/kvm/svm.c > +++ b/arch/x86/kvm/svm.c > @@ -511,8 +511,10 @@ static void skip_emulated_instruction(struct kvm_vcpu *vcpu) > { > struct vcpu_svm *svm = to_svm(vcpu); > > - if (svm->vmcb->control.next_rip != 0) > + if (svm->vmcb->control.next_rip != 0) { > + WARN_ON(!static_cpu_has(X86_FEATURE_NRIPS)); > svm->next_rip = svm->vmcb->control.next_rip; > + } > > if (!svm->next_rip) { > if (emulate_instruction(vcpu, EMULTYPE_SKIP) != > @@ -4317,7 +4319,9 @@ static int svm_check_intercept(struct kvm_vcpu *vcpu, > break; > } > > - vmcb->control.next_rip = info->next_rip; > + /* TODO: Advertise NRIPS to guest hypervisor unconditionally */ > + if (static_cpu_has(X86_FEATURE_NRIPS)) > + vmcb->control.next_rip = info->next_rip; > vmcb->control.exit_code = icpt_info.exit_code; > vmexit = nested_svm_exit_handled(svm); > > Applied, thanks. paolo -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/