Re: [PATCH v2 10/10] migration: Switch to TYPE_OBJECT with object properties

[Peter Xu <peterx@redhat.com>]

On Wed, Jun 10, 2026 at 05:29:59PM +0100, Daniel P. Berrangé wrote:
> -global is/was intended for devices, primarily those which
> are created by default as part of the machine. For dynamically
> created devices the docs recommend use of -device instead
> of -global.

I wished it was called -device-global then it'll be clearer, otherwise from
an API perspective it really shouldn't be limited to qdev..

It makes sense to not call it -device-global, IMHO essentially because we
don't necessarily need to restrict it to -device.

> 
> I get that -global was exposed for migration via the inappropriate
> use of TYPE_DEVICE as a parent for TYPE_MIGRATION, but I don't
> think we should be prolonging that misuse by exposing use of
> -global for things which are QOM rather than QDev.
> 
> If we want todo that for the sake of backcompat, IMHO it should
> be deprecated so it only lives for a short while after the
> conversion to QOM.
> 
> This makes me realize that this does not implement the UserCreatable
> interface on TYPE_MIGRATION, so I'm presuming the MigrationState is
> still created internally. Perhaps we should switch to making it a
> full UserCreatable, such that -object can be used to set all migration
> parameters on the command line and -global won't be required ? 

This is what Fabiano suggested in his reply here:

https://lore.kernel.org/qemu-devel/87jys75npb.fsf@suse.de/

I wonder what's your view on that when put together the singleton series I
used to post, where I also mentioned in the reply:

https://lore.kernel.org/qemu-devel/aimtYbka4GB9Qyk6@x1.local/

If you think that's the right approach, we can try to have it to replace
-global.  -global is debug API for migration, we don't need to obsolete it.
Compat property is, which is unaffected by this.  So we can remove -global
support for migration, but it'll always be good to have a replacement for
scripts.

Thanks,

-- 
Peter Xu