vhost-vdpa: uapi to support reporting per vq size

The size of a virtqueue is a per vq configuration.
This commit introduce a new ioctl uAPI to support this flexibility.
Signed-off-by: Zhu Lingshan <lingshan.zhu@intel.com>
Message-Id: <20240202163905.8834-2-lingshan.zhu@intel.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

include/uapi/linux/vhost.h

@@ -227,4 +227,11 @@
  */
 #define VHOST_VDPA_GET_VRING_DESC_GROUP	_IOWR(VHOST_VIRTIO, 0x7F,	\
 					      struct vhost_vring_state)
+
+/* Get the queue size of a specific virtqueue.
+ * userspace set the vring index in vhost_vring_state.index
+ * kernel set the queue size in vhost_vring_state.num
+ */
+#define VHOST_VDPA_GET_VRING_SIZE	_IOWR(VHOST_VIRTIO, 0x80,	\
+					      struct vhost_vring_state)
 #endif