Re: [PATCH V3] vmx/nmi: Do not use self_nmi() in VMEXIT handler

[Andrew Cooper <andrew.cooper3@citrix.com>]

On 28/02/13 09:58, Jan Beulich wrote:
>>>> On 22.11.12 at 17:12, Jan Beulich wrote:
>>>>> On 22.11.12 at 17:05, Andrew Cooper <andrew.cooper3@citrix.com> wrote:
>>> On 22/11/12 15:55, Jan Beulich wrote:
>>>>>>> On 22.11.12 at 16:37, Andrew Cooper <andrew.cooper3@citrix.com> wrote:
>>>>> A quick solution would be to execute a noop function with
>>>>> run_in_exception_handler().  Alternatively, I can code enable_nmi() or
>>>>> so which does an inline iret to itself.  Which of these would you prefer?
>>>> I would actually consider avoiding to run softirqs altogether in that
>>>> case, just like native Linux doesn't do any event or scheduler
>>>> processing in that case.
>>> That would probably be the easiest solution.
>>>
>>> I was already going to do the same for the rentrant NMI and MCE handling
>>> case (and also the process pending upcalls checking), due to the
>>> complexities of fixing the race condition at the end of the handler.
>>>
>>> Unfortunately, I don't think I have time to look at this issue
>>> immediately, but if it is ok to wait till the beginning of next week, I
>> That's fine of course.
> So that was 3 months ago, and we're likely going to need to do
> further unfixed releases if this won't move forward. Can you
> estimate whether you'll be able to get back to this?
>
> Jan
>

With the new enable_nmi() function, I can spin a workaround patch quite
quickly, and will try to get that done this week.  The remainder of the
reentrant tangle is still happening very slowly.

~Andrew