Re: migration: broken snapshot saves appear on s390 when small fields in migration stream removed

[Thomas Huth]

On 14/07/2020 16.29, Claudio Fontana wrote:
> Hello,
> 
> I have some tiny progress in narrowing down this issue, possibly a qcow2 
> issue, still unclear,
> but involving Kevin Wolf and Max Reitz.
> 
> 
> The reproducer again:
> 
>> --------------------------------------------cut-------------------------------------------
>> diff --git a/cpus.c b/cpus.c
>> index 41d1c5099f..443b88697a 100644
>> --- a/cpus.c
>> +++ b/cpus.c
>> @@ -643,7 +643,7 @@ static void qemu_account_warp_timer(void)
>>  
>>  static bool icount_state_needed(void *opaque)
>>  {
>> -    return use_icount;
>> +    return 0;
>>  }
>>  
>>  static bool warp_timer_state_needed(void *opaque)
>> --------------------------------------------cut-------------------------------------------
> 
> This issue for now appears on s390 only:
> 
> On s390 hardware, test 267 fails (both kvm and tcg) in the qcow2 backing file 
> part, with broken migration stream data in the s390-skeys vmsave (old style).
[...]
> If someone has a good idea let me know - first attempts to reproduce on x86 
> failed, but maybe more work could lead to it.

Two questions:

1) Can you also reproduce the issue manually, without running iotest
267? ... I tried, but so far I failed.

2) Since all the information so far sounds like the problem could be
elsewhere in the code, and the skeys just catch it by accident ... have
you tried running with valgrind? Maybe it catches something useful?

 Thomas