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

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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>
This commit is contained in:
Bandan Das 2015-06-11 02:05:33 -04:00 committed by Paolo Bonzini
parent 0b8ba4a2b6
commit f104765b4f
1 changed files with 6 additions and 2 deletions
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8
arch/x86/kvm/svm.c
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@ -511,8 +511,10 @@ static void skip_emulated_instruction(struct kvm_vcpu *vcpu)
{ {
struct vcpu_svm *svm = to_svm(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; svm->next_rip = svm->vmcb->control.next_rip;
}
if (!svm->next_rip) { if (!svm->next_rip) {
if (emulate_instruction(vcpu, EMULTYPE_SKIP) != if (emulate_instruction(vcpu, EMULTYPE_SKIP) !=
@ -4329,7 +4331,9 @@ static int svm_check_intercept(struct kvm_vcpu *vcpu,
break; 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; vmcb->control.exit_code = icpt_info.exit_code;
vmexit = nested_svm_exit_handled(svm); vmexit = nested_svm_exit_handled(svm);