vhost: forbid change vq groups ASID if DRIVER_OK is set

Only vdpa_sim support it.  Forbid this behaviour as there is no use for
it right now, we can always enable it in the future with a feature flag.

Acked-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Message-Id: <20260119143306.1818855-7-eperezma@redhat.com>

Author: eugpermar

drivers/vhost/vdpa.c

@@ -682,6 +682,8 @@ static long vhost_vdpa_vring_ioctl(struct vhost_vdpa *v, unsigned int cmd,
 			return -EFAULT;
 		if (idx >= vdpa->ngroups || s.num >= vdpa->nas)
 			return -EINVAL;
+		if (ops->get_status(vdpa) & VIRTIO_CONFIG_S_DRIVER_OK)
+			return -EBUSY;
 		if (!ops->set_group_asid)
 			return -EOPNOTSUPP;
 		return ops->set_group_asid(vdpa, idx, s.num);