KVM: nSVM: Check for NRIPS support before updating control field (f104765b) · Commits · 戴 / test

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 <bsd@redhat.com> Signed-off-by:

Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/svm.c

+6 −2

Original line number	Diff line number	Diff line
		@@ -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) !=
		@@ -4329,6 +4331,8 @@ static int svm_check_intercept(struct kvm_vcpu *vcpu,
		break;
		}

		/* 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);

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