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

commit f104765b4f81fd74d69e0eb161e89096deade2db upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 6 insertions, 2 deletions

diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index 9afa233b5482..4911bf19122b 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);