Re: [Qemu-devel] [PULL 08/17] block: Assert no write requests under BDRV_O_INCOMING

[Laurent Vivier <lvivier@redhat.com>]

On 19/02/2016 10:17, Kevin Wolf wrote:
> Am 18.02.2016 um 17:03 hat Laurent Vivier geschrieben:
>> Hi,
>>
>> this commit breaks incoming migration case:
>>
>> qemu-system-ppc64 XXX -incoming tcp:0:4444
>> qemu-system-ppc64: .../qemu/block/io.c:1304: bdrv_co_do_pwritev:
>> Assertion `!(bs->open_flags & 0x0800)' failed.
>>
>> Without "-incoming", the same command line boots fine.
>>
>> Are you aware of the problem?
> 
> No, and with no other command line options it works for me:
> 
>     $ ppc64-softmmu/qemu-system-ppc64 -incoming tcp::4444
> 
> I have also tested somewhat more realistic cases on x86 (including
> performing actual migrations) before committing the patch, so it's not
> generally broken.
> 
> Can you please give the full command line and the stack backtrace? I
> think you're seeing a bug where some PPC hardware tries to read (or
> access anyway) the image before the migration has completed. This is for
> obvious reasons wrong (the contents may still change until the VM is
> handed over).

It happens before the migration has started, as soon as I start qemu
with "-incoming" parameter.

The simplified command line is:

qemu-system-ppc64
-drive file=rhel7.2-le.qcow2,format=qcow2,snapshot=on
-incoming tcp:0:4444

The problem seems coming from "snapshot=on".

Laurent