vDPA: introduce get_vq_size to vdpa_config_ops

This commit introduces a new interface get_vq_size to
vDPA config ops, this new interface intends to report
the size of a specific virtqueue
Signed-off-by: Zhu Lingshan <lingshan.zhu@intel.com>
Message-Id: <20240202163905.8834-3-lingshan.zhu@intel.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

drivers/vhost/vdpa.c

@@ -687,6 +687,14 @@ static long vhost_vdpa_vring_ioctl(struct vhost_vdpa *v, unsigned int cmd,
 		if (!ops->set_group_asid)
 			return -EOPNOTSUPP;
 		return ops->set_group_asid(vdpa, idx, s.num);
+	case VHOST_VDPA_GET_VRING_SIZE:
+		if (!ops->get_vq_size)
+			return -EOPNOTSUPP;
+		s.index = idx;
+		s.num = ops->get_vq_size(vdpa, idx);
+		if (copy_to_user(argp, &s, sizeof(s)))
+			return -EFAULT;
+		return 0;
 	case VHOST_GET_VRING_BASE:
 		r = ops->get_vq_state(v->vdpa, idx, &vq_state);
 		if (r)

include/linux/vdpa.h

@@ -195,6 +195,10 @@ struct vdpa_map_file {
  *				@idx: virtqueue index
  *				Returns int: irq number of a virtqueue,
  *				negative number if no irq assigned.
+ * @get_vq_size:		Get the size of a specific virtqueue (optional)
+ *				@vdev: vdpa device
+ *				@idx: virtqueue index
+ *				Return u16: the size of the virtqueue
  * @get_vq_align:		Get the virtqueue align requirement
  *				for the device
  *				@vdev: vdpa device
@@ -386,6 +390,7 @@ struct vdpa_config_ops {
 	(*get_vq_notification)(struct vdpa_device *vdev, u16 idx);
 	/* vq irq is not expected to be changed once DRIVER_OK is set */
 	int (*get_vq_irq)(struct vdpa_device *vdev, u16 idx);
+	u16 (*get_vq_size)(struct vdpa_device *vdev, u16 idx);
 
 	/* Device ops */
 	u32 (*get_vq_align)(struct vdpa_device *vdev);