vhost-vdpa: introduce uAPI to get the number of address spaces

This patch introduces the uAPI for getting the number of address
spaces supported by this vDPA device.
Signed-off-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Gautam Dawar <gdawar@xilinx.com>
Message-Id: <20220330180436.24644-13-gdawar@xilinx.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

drivers/vhost/vdpa.c

@@ -563,6 +563,9 @@ static long vhost_vdpa_unlocked_ioctl(struct file *filep,
 		r = copy_to_user(argp, &v->vdpa->ngroups,
 				 sizeof(v->vdpa->ngroups));
 		break;
+	case VHOST_VDPA_GET_AS_NUM:
+		r = copy_to_user(argp, &v->vdpa->nas, sizeof(v->vdpa->nas));
+		break;
 	case VHOST_SET_LOG_BASE:
 	case VHOST_SET_LOG_FD:
 		r = -ENOIOCTLCMD;

include/uapi/linux/vhost.h

@@ -154,4 +154,6 @@
 /* Get the number of virtqueue groups. */
 #define VHOST_VDPA_GET_GROUP_NUM	_IOR(VHOST_VIRTIO, 0x81, __u32)
 
+/* Get the number of address spaces. */
+#define VHOST_VDPA_GET_AS_NUM		_IOR(VHOST_VIRTIO, 0x7A, unsigned int)
 #endif