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Re: migration: broken snapshot saves appear on s390 when small fields in
From: |
Claudio Fontana |
Subject: |
Re: migration: broken snapshot saves appear on s390 when small fields in migration stream removed |
Date: |
Wed, 15 Jul 2020 13:10:22 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.4.1 |
Hi Thomas,
On 7/14/20 4:35 PM, Thomas Huth wrote:
> 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.
>
small update: in the GOOD case (enough padding added) a qcow_merge() is
triggered for the last write of 16202 bytes.
In the BAD case (not enough padding added) a qcow_merge() is not triggered for
the last write of 16201 bytes.
Note: manually flushing with qemu_fflush in s390-skeys vmsave also works (maybe
got lost in the noise).
> Two questions:
>
> 1) Can you also reproduce the issue manually, without running iotest
> 267? ... I tried, but so far I failed.
Thanks for the suggestion, will try.
>
> 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?
Nothing yet, but will fiddle with the options a bit more.
>
> Thomas
>
Ciao,
Claudio
- migration: broken snapshot saves appear on s390 when small fields in migration stream removed, Claudio Fontana, 2020/07/12
- Re: migration: broken snapshot saves appear on s390 when small fields in migration stream removed, Paolo Bonzini, 2020/07/12
- Re: migration: broken snapshot saves appear on s390 when small fields in migration stream removed, Claudio Fontana, 2020/07/13
- Re: migration: broken snapshot saves appear on s390 when small fields in migration stream removed, Claudio Fontana, 2020/07/14
- Re: migration: broken snapshot saves appear on s390 when small fields in migration stream removed, Thomas Huth, 2020/07/14
- Re: migration: broken snapshot saves appear on s390 when small fields in migration stream removed,
Claudio Fontana <=
- Re: migration: broken snapshot saves appear on s390 when small fields in migration stream removed, Claudio Fontana, 2020/07/15
- Re: migration: broken snapshot saves appear on s390 when small fields in migration stream removed, Claudio Fontana, 2020/07/16
- Re: migration: broken snapshot saves appear on s390 when small fields in migration stream removed, Claudio Fontana, 2020/07/20
- Re: migration: broken snapshot saves appear on s390 when small fields in migration stream removed, Claudio Fontana, 2020/07/21
- Re: migration: broken snapshot saves appear on s390 when small fields in migration stream removed, Bruce Rogers, 2020/07/27
- Re: migration: broken snapshot saves appear on s390 when small fields in migration stream removed, Vladimir Sementsov-Ogievskiy, 2020/07/28
- Re: migration: broken snapshot saves appear on s390 when small fields in migration stream removed, Vladimir Sementsov-Ogievskiy, 2020/07/28
- Re: migration: broken snapshot saves appear on s390 when small fields in migration stream removed, Bruce Rogers, 2020/07/28
- Re: migration: broken snapshot saves appear on s390 when small fields in migration stream removed, Max Reitz, 2020/07/28
- Re: migration: broken snapshot saves appear on s390 when small fields in migration stream removed, Vladimir Sementsov-Ogievskiy, 2020/07/28