Sean Christopherson <sean.j.christopherson@xxxxxxxxx> writes:
> On Thu, Aug 01, 2019 at 07:14:16AM +0200, Vitaly Kuznetsov wrote:
>> Regardless of the way how we skip instruction, interrupt shadow needs to be
>> cleared.
>>
>> Signed-off-by: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>
>> Reviewed-by: Jim Mattson <jmattson@xxxxxxxxxx>
>> ---
>> arch/x86/kvm/svm.c | 4 +++-
>> 1 file changed, 3 insertions(+), 1 deletion(-)
>>
>> diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
>> index 80f576e05112..7c7dff3f461f 100644
>> --- a/arch/x86/kvm/svm.c
>> +++ b/arch/x86/kvm/svm.c
>> @@ -784,13 +784,15 @@ static void skip_emulated_instruction(struct kvm_vcpu *vcpu)
>> EMULATE_DONE)
>> pr_err_once("KVM: %s: unable to skip instruction\n",
>> __func__);
>> - return;
>> + goto clear_int_shadow;
>
> A better fix would be to clear the interrupt shadow in x86_emulate_instruction()
> after updating RIP for EMULTYPE_SKIP. VMX has this same flaw when running
> nested as handle_ept_misconfig() also expects the interrupt shadow to be
> handled by kvm_emulate_instruction(). Clearing the shadow if and only if
> the skipping is successful also means KVM isn't incorrectly zapping the
> shadow when emulation fails.
Oh, nice catch actually! Will do in v2.
--
Vitaly
