Re: [PATCH 2/2] virtio: Drop out of coroutine context in virtio_load()

[Juan Quintela]

Michael Tokarev <mjt@tls.msk.ru> wrote:
> 05.09.2023 17:50, Kevin Wolf wrote:
>> virtio_load() as a whole should run in coroutine context because it
>> reads from the migration stream and we don't want this to block.
>> However, it calls virtio_set_features_nocheck() and devices don't
>> expect their .set_features callback to run in a coroutine and therefore
>> call functions that may not be called in coroutine context. To fix this,
>> drop out of coroutine context for calling virtio_set_features_nocheck().
> ...
>> Cc: qemu-stable@nongnu.org
>> Buglink: https://issues.redhat.com/browse/RHEL-832
>> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
>
> It looks like this change caused an interesting regression,
>   https://gitlab.com/qemu-project/qemu/-/issues/1933
> at least in -stable.  Can you take a look please?
>
> BTW, Kevin, do you have account @gitlab?

Dunno what is going on here, but failing postcopy is weird.

2023-10-12T06:23:44.354387Z qemu-system-x86_64: warning: TSC frequency mismatch 
between VM (2892749 kHz) and host (2799999 kHz), and TSC scaling unavailable 
2023-10-12T06:23:44.354538Z qemu-system-x86_64: warning: TSC frequency mismatch 
between VM (2892749 kHz) and host (2799999 kHz), and TSC scaling unavailable

I hope/guess that the problem is not TSC related?

i.e. does other tests work between this two machines?

Once discarding that, we get on source:

2023-10-12 06:23:43.412+0000: initiating migration

2023-10-12T06:23:44.362392Z qemu-system-x86_64: failed to save
SaveStateEntry with id(name): 3(ram): -5

So migration was aborted, and -5 is EIO on my system.
So we are having trouble here with a write() somewhere.

Later, Juan.

> Thanks,
>
> /mjt