vhost: support PACKED when setting-getting vring_base

Use the right structs for PACKED or split vqs when setting and
getting the vring base.

Fixes: 4c8cf318 ("vhost: introduce vDPA-based backend")
Signed-off-by: Shannon Nelson <shannon.nelson@amd.com>
Message-Id: <20230424225031.18947-3-shannon.nelson@amd.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: Jason Wang <jasowang@redhat.com>

drivers/vhost/vhost.c

@@ -1600,16 +1600,24 @@ long vhost_vring_ioctl(struct vhost_dev *d, unsigned int ioctl, void __user *arg
 			r = -EFAULT;
 			break;
 		}
+		if (vhost_has_feature(vq, VIRTIO_F_RING_PACKED)) {
+			vq->last_avail_idx = s.num & 0xffff;
+			vq->last_used_idx = (s.num >> 16) & 0xffff;
+		} else {
 			if (s.num > 0xffff) {
 				r = -EINVAL;
 				break;
 			}
 			vq->last_avail_idx = s.num;
+		}
 		/* Forget the cached index value. */
 		vq->avail_idx = vq->last_avail_idx;
 		break;
 	case VHOST_GET_VRING_BASE:
 		s.index = idx;
+		if (vhost_has_feature(vq, VIRTIO_F_RING_PACKED))
+			s.num = (u32)vq->last_avail_idx | ((u32)vq->last_used_idx << 16);
+		else
 			s.num = vq->last_avail_idx;
 		if (copy_to_user(argp, &s, sizeof s))
 			r = -EFAULT;

drivers/vhost/vhost.h

@@ -92,13 +92,17 @@ struct vhost_virtqueue {
 	/* The routine to call when the Guest pings us, or timeout. */
 	vhost_work_fn_t handle_kick;
 
-	/* Last available index we saw. */
+	/* Last available index we saw.
+	 * Values are limited to 0x7fff, and the high bit is used as
+	 * a wrap counter when using VIRTIO_F_RING_PACKED. */
 	u16 last_avail_idx;
 
 	/* Caches available index value from user. */
 	u16 avail_idx;
 
-	/* Last index we used. */
+	/* Last index we used.
+	 * Values are limited to 0x7fff, and the high bit is used as
+	 * a wrap counter when using VIRTIO_F_RING_PACKED. */
 	u16 last_used_idx;
 
 	/* Used flags */