From mboxrd@z Thu Jan 1 00:00:00 1970 From: Bandan Das Subject: [PATCH] KVM: nSVM: Check for NRIPS support before updating control field Date: Thu, 11 Jun 2015 02:05:33 -0400 Message-ID: Mime-Version: 1.0 Content-Type: text/plain Cc: linux-kernel@vger.kernel.org, Paolo Bonzini , Radim Krcmar , jan.kiszka@siemens.com To: kvm@vger.kernel.org Return-path: Received: from mx1.redhat.com ([209.132.183.28]:39183 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750897AbbFKGFf (ORCPT ); Thu, 11 Jun 2015 02:05:35 -0400 Sender: kvm-owner@vger.kernel.org List-ID: 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); -- 2.1.0