Re: Supsend/resume regression in c995b4 WAS: Re: [Qemu-devel] [PATCH] Fix migration uint8 arrys handled

[Jan Kiszka <jan.kiszka@siemens.com>]

On 2011-03-22 12:56, Stefan Berger wrote:
> On 03/22/2011 07:50 AM, Stefan Berger wrote:
>> On 03/22/2011 06:40 AM, Avi Kivity wrote:
>>> On 03/22/2011 12:23 PM, Stefan Berger wrote:
>>>> On 03/22/2011 05:28 AM, Avi Kivity wrote:
>>>>> On 03/22/2011 03:46 AM, Anthony Liguori wrote:
>>>>>> On 03/21/2011 07:25 PM, Stefan Berger wrote:
>>>>>>> On 03/15/2011 10:53 AM, Juan Quintela wrote:
>>>>>>>> commit 82fa39b75181b730d6d4d09f443bd26bcfcd045c
>>>>>>>>
>>>>>>>> only contains half of the fix.  It forgots the save state fix for
>>>>>>>> UINT8 indexes.
>>>>>>>>
>>>>>>>> Anthony, please apply, without this migration using hpet is broken.
>>>>>>>> (only current user).
>>>>>>> I have just been bisecting the code (from the tip) due to 
>>>>>>> suspend/resume problems and it looks like commit 82fa39b7 is 
>>>>>>> introducing the suspend/resume problem I am seeing (frozen screen).
>>>>>>
>>>>>> It's in tip now.
>>>>>
>>>>> Great, spent some lovely time bisecting and fixing it as well.
>>>>>
>>>> It doesn't work better now than it did before... Trying a 
>>>> suspend/resume while in grub leaves me with a black screen upon 
>>>> resume...
>>>
>>> Well, it fixed it for me (autotest migration tests).
>>>
>>> Do you mean that 82fa39b7^ works but b784421ce4c doesn't?  What about 
>>> b784421ce4c^ with 82fa39b7 reverted?  That will rule out some other bug.
>>>
>> b784421 works for me. It's the tip that is again broken for 
>> suspend/resume, this time pointing to
>>
>> c995b495b9d6e60ab1e390bd398a22425d0b3c8c is the first bad commit
>> commit c995b495b9d6e60ab1e390bd398a22425d0b3c8c
>> Author: Jan Kiszka <jan.kiszka@siemens.com>
>> Date:   Tue Mar 15 12:26:22 2011 +0100
>>
>>     x86: Save/restore PAT MSR
>>
>>     Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
>>     Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
>>
>> diff --git a/target-i386/machine.c b/target-i386/machine.c
>> index d78eceb..6384f54 100644
>> --- a/target-i386/machine.c
>> +++ b/target-i386/machine.c
>> @@ -491,6 +491,8 @@ static const VMStateDescription vmstate_cpu = {
>>          VMSTATE_UINT64_V(xcr0, CPUState, 12),
>>          VMSTATE_UINT64_V(xstate_bv, CPUState, 12),
>>          VMSTATE_YMMH_REGS_VARS(ymmh_regs, CPUState, CPU_NB_REGS, 12),
>> +
>> +        VMSTATE_UINT64_V(pat, CPUState, 13),
>>          VMSTATE_END_OF_LIST()
>>          /* The above list is not sorted /wrt version numbers, watch 
>> out! */
>>      },
>>
>> Doesn't look bad, but I get a black screen when resuming while in grub.
>>
> I think that patch was probably not necessary:
> 
> target-i386/machine.c line 452 has this:
> 
>          VMSTATE_UINT64_V(pat, CPUState, 5),
> 
> then again in line 495:
> 
>          VMSTATE_UINT64_V(pat, CPUState, 13),
> 

Ouch, indeed. Moreover, CPU_SAVE_VERSION was not updated (likely the
reason for the breakage). Thanks for debugging this!

Anthony (or whoever), please revert this unneeded commit in qemu.git.

We had a few migration related regressions recently. Do we have
sufficient test cases in autotest for them? Also for migrating from
older to the latest version?

Jan

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