Re: [Xen-devel] Xen-unstable 4.8: HVM domain_crash called from emulate.c:144 RIP: c000:[<000000000000336a>]

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 15.06.16 at 14:00, <linux@xxxxxxxxxxxxxx> wrote:
> Wednesday, June 15, 2016, 12:12:37 PM, you wrote:
>>>>> On 15.06.16 at 11:38, <linux@xxxxxxxxxxxxxx> wrote:
>>> Wednesday, June 15, 2016, 10:57:03 AM, you wrote:
>>>> Wednesday, June 15, 2016, 10:29:37 AM, you wrote:
>>>>>>>> On 15.06.16 at 01:49, <linux@xxxxxxxxxxxxxx> wrote:
>>>>>> Just tested latest xen-unstable 4.8 (xen_changeset git:d337764),
>>>>>> but one of the latest commits seems to have broken boot of HVM guests
>>>>>> (using qemu-xen) previous build with xen_changeset git:6e908ee worked 
>>>>>> fine.
>>> 
>>>>> Primary suspects would seem to be 67fc274bbe and bfa84968b2,
>>>>> but (obviously) I didn't see any issues with them in my own
>>>>> testing, so could you
>>>>> - instead of doing a full bisect, revert just those two
>>> 
>>>> Will give reverting that a shot.
>>> 
>>> Reverting bfa84968b2 is sufficient.
> 
>> Could you give this wild guess a try on top of the tree without the
>> revert?
> 
>> --- unstable.orig/xen/arch/x86/hvm/emulate.c
>> +++ unstable/xen/arch/x86/hvm/emulate.c
>> @@ -1180,7 +1180,7 @@ static int hvmemul_rep_movs(
>>          pfec |= PFEC_user_mode;
>>  
>>      bytes = PAGE_SIZE - (saddr & ~PAGE_MASK);
> -    if ( vio->>mmio_access.read_access &&
> +    if ( vio->>mmio_access.read_access && !vio->mmio_access.write_access &&
>>           (vio->mmio_gla == (saddr & PAGE_MASK)) &&
>>           bytes >= bytes_per_rep )
>>      {
> 
> Unfortunately still crashes.

Thanks for trying. Which basically just leaves the p.count > *reps
part in that domain_crash() condition, as that's the only other thing
involved in that check which said commit could have an effect on (as
far as I can tell at least). Would you be up for another experiment,
removing that one line? Other things to try (just to understand the
issue) would be to
- revert only each half of said commit individually (the two hunks
  really are independent),
- remove just the two latch_linear_to_phys() calls.

Apart from that, and just to see whether there are other differences
between your guest(s) and mine, could you post a guest config from
one that's affected?

Jan


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