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

[Max Reitz]

On 28.07.20 13:35, Paolo Bonzini wrote:
> On 28/07/20 13:33, Vladimir Sementsov-Ogievskiy wrote:
>>> Thanks for both your investigation.  Does the attached patch help?
>>
>> For me, the reproducer is fixed with your patch.
> 
> Is it possible to make a quick testcase using qemu-io?

This seems to work:

$ qemu-img create -f qcow2 -o cluster_size=512 base.qcow2 512
$ qemu-img create -f qcow2 -o cluster_size=512 -F qcow2 -b base.qcow2 \
  top.qcow2 1024
$ qemu-io -c 'write -P 42 0 512' top.qcow2
$ qemu-io -c 'read -v 0 1024' top.qcow2

That should print 512 times “2a” and then 512 times “00”, but beyond
512, the buffer stays uninitialized; instead, the first 512 bytes are
zeroed.  (With the patch, it works as expected.)

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