x86: KVM: clear interrupt shadow on EMULTYPE_SKIP

When doing x86_emulate_instruction(EMULTYPE_SKIP) interrupt shadow has to
be cleared if and only if the skipping is successful.

There are two immediate issues:
- In SVM skip_emulated_instruction() we are not zapping interrupt shadow
  in case kvm_emulate_instruction(EMULTYPE_SKIP) is used to advance RIP
  (!nrpip_save).
- In VMX handle_ept_misconfig() when running as a nested hypervisor we
  (static_cpu_has(X86_FEATURE_HYPERVISOR) case) forget to clear interrupt
  shadow.

Note that we intentionally don't handle the case when the skipped
instruction is supposed to prolong the interrupt shadow ("MOV/POP SS") as
skip-emulation of those instructions should not happen under normal
circumstances.

Suggested-by: Sean Christopherson <sean.j.christopherson@intel.com>
Reviewed-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 73825ab..90a895d 100644 (file)
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -6546,6 +6546,7 @@ int x86_emulate_instruction(struct kvm_vcpu *vcpu,
                kvm_rip_write(vcpu, ctxt->_eip);
                if (ctxt->eflags & X86_EFLAGS_RF)
                        kvm_set_rflags(vcpu, ctxt->eflags & ~X86_EFLAGS_RF);
+               kvm_x86_ops->set_interrupt_shadow(vcpu, 0);
                return EMULATE_DONE;
        }