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

[Sander Eikelenboom <linux@eikelenboom.it>]

Wednesday, June 15, 2016, 2:48:55 PM, you wrote:

>>>> On 15.06.16 at 14:00, <linux@eikelenboom.it> wrote:
>> Wednesday, June 15, 2016, 12:12:37 PM, you wrote:
>>>>>> On 15.06.16 at 11:38, <linux@eikelenboom.it> 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@eikelenboom.it> 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.

Will try some of that and let you know.

> 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?

Hope you are not too disappointed it's rather sparse:

builder='hvm'
device_model_version = 'qemu-xen'
device_model_user = 'root'
memory = 512
name = 'test_guest'
vcpus = 4
cpu_weight = 768
vif = [ 'bridge=xen_bridge, ip=192.168.1.15, mac=00:16:3E:C4:72:83, model=e1000' ]
disk = [ 'phy:/dev/xen_vms/test_guest1,hda,w', 'phy:/dev/xen_vms/test_guest2,hdb,w' ]
on_crash = 'preserve'
boot='c'
vnc=0
serial='pty'

Both dom0 and guest run Debian Jessie, as said platform is AMD, running a 
4.7-rc3ish kernel.


> Jan



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