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

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 22/11/12 16:12, Jan Beulich wrote:
>>>> On 22.11.12 at 17:05, Andrew Cooper <andrew.cooper3@xxxxxxxxxx> wrote:
>> On 22/11/12 15:55, Jan Beulich wrote:
>>>>>> On 22.11.12 at 16:37, Andrew Cooper <andrew.cooper3@xxxxxxxxxx> 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.
>
>> can roll it into the main dev work for the other NMI/MCE work.
> Hmm, that would mean it's going to be more difficult to backport.
> I'd prefer having this in as simple a fashion as possible in the
> patch here, and then have your other patch(es) build on top of
> that.
>
> Jan
>

I will ensure that the fix for this is suitably separate in the patch
series, and in the easiest backportable form.

-- 
Andrew Cooper - Dom0 Kernel Engineer, Citrix XenServer
T: +44 (0)1223 225 900, http://www.citrix.com


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