Re: [PATCH v3 0/5] Fix "virtio-gpu: fix scanout migration post-load"

[Peter Xu <peterx@redhat.com>]

On Wed, May 15, 2024 at 06:15:51PM +0400, marcandre.lureau@redhat.com wrote:
> From: Marc-André Lureau <marcandre.lureau@redhat.com>
> 
> Hi,
> 
> The aforementioned patch breaks virtio-gpu device migrations for versions
> pre-9.0/9.0, both forwards and backwards. Versioning of `VMS_STRUCT` is more
> complex than it may initially appear, as evidenced in the problematic commit
> dfcf74fa68c ("virtio-gpu: fix scanout migration post-load").
> 
> v2:
>  - use a manual version field test (instead of the more complex struct variant)
> 
> v3:
>  - introduce machine_check_version()
>  - drop the VMSD version, and use machine version field test

Thanks for trying this out already.

Last time I mentioned this may for the long term because I remember Dan and
Thomas were trying to work on some machine deprecation work, and maybe such
things may collapse with that work (and perhaps easier with that work
landed, too?).  Just to copy them both here so we know where we are now, as
I didn't follow that discussion.  IOW, patch 3/4 may need separate review
from outside migration..

The simpler solution is we stick with the customized field and simple fix
to the issue first, then whenever we have that new helper later we simply
use the new helper to replace the old, alongside we can drop the new field
/ property too as long as it is declared with "x-".  Might be easier to
backport too in this case.  Marc-Andre, what do you think?

Thanks,

-- 
Peter Xu