Re: [Qemu-devel] [PATCH 0/3] non-migratable devices

[Paolo Bonzini]

On 07/08/2011 01:47 PM, Gerd Hoffmann wrote:
> > scsi-cd is new in 0.15, older versions have scsi-disk only. That's why
> > we should take the occasion to add the empty vmstate at least to it.
>
> Ok, good opportunity in that specific case.
>
> > For other devices, it's better to make the breakage in a single version.
> > It also allows to make 0.15 the "flag day" where each device shall have
> > a VMState or the entire VM will not be migratable.
>
> Not that easy given that we didn't fully migrate to vmstate yet,
> otherwise we could simply fail migration in case we find any device with
> qdev->vmsd == NULL.

You can always add

#define VMSD_NONE  ((const VMStateDescription *) 1)

> > If desired, in the
> > future we can revert this behavior for pc-0.14 and earlier machines.
>
> And I'm still looking for a sane way to handle *this*.

One possibility is to add device name remapping to machine types, like 
"ide is actually ide-0.14 when using pc-0.14" and put a different 
VMState in ide-0.14.

Paolo