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

[Paolo Bonzini]

On 12/07/20 12:00, Claudio Fontana wrote:
> Note: only the === -blockdev with a backing file === part of test 267 fails. 
> -blockdev with NBD is ok, like all the rest.
> 
> 
> Interesting facts about s390 in particular: its save/load code includes the 
> transfer of "storage keys",
> which include a buffer of 32768 bytes of keydata in the stream.
> 
> The code (hw/s390x/s390-skeys.c),
> is modeled similarly to RAM transfer (like in migration/ram.c), with an EOS 
> (end of stream) marker.
> 
> Countrary to RAM transfer code though, after qemu_put_be64(f, EOS), the s390 
> code does not qemu_fflush(f).

1) Are there unexpected differences in the migration stream?  That is,
you could modify qcow2.c to fopen/fwrite/fclose the bytes as they're
written and read, and see if something does not match.

2) If it matches, are there unexpected differences other than the lack
of icount section when you apply the reproducer patch?

The fflush part makes me put more hope in the first, but both could help
you debug it.

Thanks,

Paolo