Re: [PATCH RFC 3/5] x86: KVM: svm: clear interrupt shadow on all paths in skip_emulated_instruction()

Vitaly Kuznetsov
2019-07-31T13:50:38Z

Jim Mattson <jmattson@google.com> writes:

> On Thu, Jun 20, 2019 at 4:02 AM Vitaly Kuznetsov <vkuznets@redhat.com> wrote:
>>
>> Regardless of the way how we skip instruction, interrupt shadow needs to be
>> cleared.
>
> This change is definitely an improvement, but the existing code seems
> to assume that we never call skip_emulated_instruction on a
> POP-SS/MOV-to-SS/STI. Is that enforced anywhere?

(before I send v1 of the series) I looked at the current code and I
don't think it is enforced, however, VMX version does the same and
honestly I can't think of a situation when we would be doing 'skip' for
such an instruction.... and there's nothing we can easily enforce from
skip_emulated_instruction() as we have no idea what the instruction
is...

I can of course be totally wrong and would appreciate if someone more
knowledgeable chimes in :-)

--
Vitaly