Re: [Qemu-devel] [PATCH V2 4/8] virtio-pci: fix 1.0 virtqueue migration

[Cornelia Huck]

On Mon, 7 Sep 2015 15:39:59 +0800
Jason Wang <address@hidden> wrote:

> On 09/02/2015 07:06 PM, Cornelia Huck wrote:
> > On Wed,  2 Sep 2015 11:25:21 +0800
> > Jason Wang <address@hidden> wrote:

> >> +static int get_extra_state(QEMUFile *f, void *pv, size_t size)
> >> +{
> >> +    VirtIODevice *vdev = pv;
> >> +    BusState *qbus = qdev_get_parent_bus(DEVICE(vdev));
> >> +    VirtioBusClass *k = VIRTIO_BUS_GET_CLASS(qbus);
> >> +    int ret = 0;
> >> +
> >> +    ret = k->load_extra_state(qbus->parent, f);
> > Should we check for ->load_extra_state() and return failure if it does
> > not exist?
> 
> I think checking the existence of has_extra_state() in
> virtio_extra_state_needed() is enough for this? Or is there anything I miss?

The has_extra_state() callback is called by the sender, not by the
receiver.

If the other side sent the extra state but we can't handle it, I think
it would be better to fail the migration than to crash. Still broken
code, but probably easier to debug :)