Re: Crash of guest with nested vmx with Unknown nested vmexit reason 80000021.

["Jan Beulich" <JBeulich@suse.com>]

>>> On 16.10.14 at 08:18, <yang.z.zhang@intel.com> wrote:
> Sorry for the later reply. Yes, this is a known issue to me but I didn't 
> have time to cook a patch fix it. As Jan pointed out, the NMI handling logic 
> is wrong in current nested logic. But it is not a trivial task to fix them. I 
> will do it once I have the time or if you are interesting in it, a patch from 
> you is welcome.

If you were to at least comment on the two possible routes I
outlined (quoted below), I could see to get to this (considering
that the issue - as you point out subsequently - got brought up
more than half a year ago the first time, and is still unaddressed)
at least if the vmx_idtv_reinject() related route would be a
possible one.

Jan

>>>> From: Jan Beulich [mailto:JBeulich@suse.com]
>>>> So the problem here is that
>>>> 
>>>>> (XEN) Interruptibility=0008 ActivityState=0000
>>>> VMX_INTR_SHADOW_NMI is set while
>>>> 
>>>>> (XEN) PinBased=0000003f CPUBased=b6b9e5fa SecondaryExec=000004eb
>>>> PIN_BASED_VIRTUAL_NMIS is active and
>>>> 
>>>>> (XEN) VMEntry: intr_info=80000202 errcode=5d021101 ilen=00000003
>>>>> (XEN) VMExit: intr_info=00000000 errcode=00000000 ilen=00000003
>>>>> (XEN)         reason=80000021 qualification=00000000
>>>>> (XEN) IDTVectoring: info=80000202 errcode=00000000
>>>> an NMI is being injected. This case is explicitly mentioned in Vol
>>>> 3 section 31.7.1.2 (Resuming Guest Software after Handling an
>>>> Exception). Either there needs to be extra code in vvmx.c to clear
>>>> VMX_INTR_SHADOW_NMI (as the second sub-bullet point of the last
>>>> bullet point says), or the second half of vmx_idtv_reinject() needs
>>>> to be done without regard to nestedhvm_vcpu_in_guestmode(v) (and
>>>> maybe also without regard to EXIT_REASON_TASK_SWITCH).
>>>> 
>>>> Speaking of SDM sections: There are quite a few references in the
>>>> code that name just section numbers (in the case here, several
>>>> references to sections 25.7.1.* exist). These numbers become stale
>>>> quite quickly (here they're now 31.7.1.*), so in order to help
>>>> digging through issues like the one here, can I please ask one of
>>>> you to go through and replace (or at least amend) these numbers
>>>> with the sections' titles (which I hope won't get altered that quickly)?