vdpa: make get_vq_group and set_group_asid optional

This patch makes get_vq_group and set_group_asid optional. This is
needed to unbreak the vDPA parent that doesn't support multiple
address spaces.

Cc: Gautam Dawar <gautam.dawar@xilinx.com>
Fixes: aaca8373 ("vhost-vdpa: support ASID based IOTLB API")
Signed-off-by: Jason Wang <jasowang@redhat.com>
Message-Id: <20220609041901.2029-1-jasowang@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

drivers/vhost/vdpa.c

@@ -499,6 +499,8 @@ static long vhost_vdpa_vring_ioctl(struct vhost_vdpa *v, unsigned int cmd,
 		ops->set_vq_ready(vdpa, idx, s.num);
 		return 0;
 	case VHOST_VDPA_GET_VRING_GROUP:
+		if (!ops->get_vq_group)
+			return -EOPNOTSUPP;
 		s.index = idx;
 		s.num = ops->get_vq_group(vdpa, idx);
 		if (s.num >= vdpa->ngroups)

include/linux/vdpa.h

@@ -178,7 +178,8 @@ struct vdpa_map_file {
  *				for the device
  *				@vdev: vdpa device
  *				Returns virtqueue algin requirement
- * @get_vq_group:		Get the group id for a specific virtqueue
+ * @get_vq_group:		Get the group id for a specific
+ *				virtqueue (optional)
  *				@vdev: vdpa device
  *				@idx: virtqueue index
  *				Returns u32: group id for this virtqueue
@@ -243,7 +244,7 @@ struct vdpa_map_file {
  *				Returns the iova range supported by
  *				the device.
  * @set_group_asid:		Set address space identifier for a
- *				virtqueue group
+ *				virtqueue group (optional)
  *				@vdev: vdpa device
  *				@group: virtqueue group
  *				@asid: address space id for this group