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    Subject[PATCH v3 3/7] x86: KVM: clear interrupt shadow on EMULTYPE_SKIP
    Date
    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>
    ---
    arch/x86/kvm/x86.c | 1 +
    1 file changed, 1 insertion(+)

    diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
    index a97818b1111d..50e0b25092c7 100644
    --- a/arch/x86/kvm/x86.c
    +++ b/arch/x86/kvm/x86.c
    @@ -6539,6 +6539,7 @@ 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;
    }

    --
    2.20.1
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