Re: [Qemu-devel] [PATCH RESEND v4 16/18] savevm: check vmsd for migratability status

[Eduardo Habkost]

On Thu, May 15, 2014 at 04:05:44PM +0200, Juan Quintela wrote:
> Andreas Färber <address@hidden> wrote:
> > Am 15.05.2014 14:14, schrieb Juan Quintela:
> >> Eduardo Habkost <address@hidden> wrote:
> >>> From: Marcelo Tosatti <address@hidden>
> >>>
> >>> Check vmsd for unmigratable field, allowing migratibility status
> >>> to be modified after vmstate_register.
> >>>
> >>> Cc: Juan Quintela <address@hidden>
> >>> Signed-off-by: Marcelo Tosatti <address@hidden>
> >>> Reviewed-by: Eduardo Habkost <address@hidden>
> >>> Signed-off-by: Eduardo Habkost <address@hidden>
> >> 
> >> I agree with the patch spirt, but what happens if we want to disable
> >> migration in a device that has no VMSD?
> >
> > As the patch shows, no non-VMSD device setting no_migrate exists today.
> > Do you expect any to appear? I'm rather seeing more and more devices
> > getting converted to VMSD.
> 
> I want people to notice that.  As said, I hope that everything new uses
> VMSD.

Note that devices that have no VMSD couldn't set no_migrate before this
patch, anyway (the only way to set no_migrate was using a VMSD). The
change is not visible outside savevm.c.

If we want to disable migration in a device that has no VMSD, we will
need a savevm API change. If that ever happens, re-adding the field to
support the API change would be trivial.

-- 
Eduardo