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Commit f104765b authored by Bandan Das's avatar Bandan Das Committed by Paolo Bonzini
Browse files

KVM: nSVM: Check for NRIPS support before updating control field 



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: default avatarBandan Das <bsd@redhat.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 0b8ba4a2

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);