Re: [PATCH 1/1] Disable GUEST_INTR_STATE_STI flag before injecting NMI to guest on VMX

[Avi Kivity <avi@redhat.com>]

  On 08/27/2010 11:27 AM, Jan Kiszka wrote:
> Am 26.08.2010 22:06, Jes.Sorensen@redhat.com wrote:
>> From: Jes Sorensen<Jes.Sorensen@redhat.com>
>>
>> Injecting an NMI while GUEST_INTR_STATE_STI is set may fail,
>> which can cause an EXIT with invalid state, resulting in the
>> guest dieing.
> Very interesting. Reality obviously doesn't bother about the statement
> of the vendor [1].
>
> Just curious: is this limited to specific CPU models or actually a
> generic issue?
>

The manual states that whether a processor accepts NMIs when 
blocked-by-STI or not is processor dependent.

> Thinking about the implications: Independent of virtualization, this
> means that no code code can in any way rely on the STI shadow if there
> are NMIs present that could "consume" it. Because after return from
> those NMIs, interrupts could then be injected on the instruction that
> was originally under the shadow.
>

Wow.  Maybe we should request an interrupt window instead when 
blocked-by-STI is active instead of clearing it.

-- 
I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.