bhyve failure

[Neel Natu]

Hi Julian,

On Sat, Nov 29, 2014 at 6:31 PM, Neel Natu <neelnatu at gmail.com> wrote:
> Hi Julian,
>
> On Fri, Nov 28, 2014 at 7:36 AM, Julian Elischer <julian at freebsd.org> wrote:
>> On 11/28/14, 3:12 AM, Neel Natu wrote:
>>>
>>> Hi Julian,
>>>
>>> On Thu, Nov 27, 2014 at 7:02 AM, Julian Elischer <julian at freebsd.org>
>>> wrote:
>>>>
>>>> I added WITNESS to a kernel I've been running and during boot I got this
>>>> result:
>>>>
>>>> vm exit[0]
>>>>          reason          VMX
>>>>          rip             0xffffffff8078c1a7
>>>>          inst_length     7
>>>>          status          0
>>>>          exit_reason     2
>>>
>>> That's a triple fault (from sys/amd64/vmm/intel/vmcs.h)
>>>
>>> #define EXIT_REASON_TRIPLE_FAULT        2
>>>
>>>
>>>>          qualification   0x0000000000000000
>>>>          inst_type               0
>>>>          inst_error              0
>>>> Abort trap (core dumped)
>>>>
>>>> anyone have a decoder ring?
>>>>
>>> A few questions to narrow this down:
>>>
>>> Did you add WITNESS to the guest kernel or the host kernel when this
>>> happened?
>>
>> yes I added it to the guest kernel.. I suspect it ay be related to this,
>> especially since there was a kernel module loaded that was not recompiled.
>> I'm trying to ascertain now whether a withness kernel requires special
>> handling for its modules.
>>
>>
>>>
>>> Is this readily reproducible?
>>
>> don't know yet.
>>
>
> Its interesting that the guest went all the way to a triple fault
> instead of stopping at the double fault handler.
>
> I'll be happy to track this down if there is a reliably repro case
> (guest binaries would be sufficient).
>

I just committed a change that should let you trace every exception
seen by the guest:
https://svnweb.freebsd.org/changeset/base/276098

It will let you trace all the exceptions leading up to the triple
fault via ktr(4).

best
Neel

> best
> Neel
>
>>>
>>> Can you share the host and guest revision numbers?
>>
>>
>> guest is custom sources based on stable-10 on the same day as 10.0 was
>> released.basically whatever svn revision# was on 10.0 but on the stable
>> branch.
>> host is
>> FreeBSD 10.1-BETA1 #0 r271671: Tue Sep 16 09:31:23 PDT 2014
>>
>>
>>
>>
>>>
>>> best
>>> Neel
>>>
>>>> julian
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>>
>>