virtio_ring: disable packed ring on unsupported transports

Currently, ccw, vop and remoteproc need some legacy virtio
APIs to create or access virtio rings, which are not supported
by packed ring. So disable packed ring on these transports
for now.

Signed-off-by: Tiwei Bie <tiwei.bie@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/remoteproc/remoteproc_virtio.c

@@ -214,6 +214,16 @@ static u64 rproc_virtio_get_features(struct virtio_device *vdev)
 	return rsc->dfeatures;
 }
 
+static void rproc_transport_features(struct virtio_device *vdev)
+{
+	/*
+	 * Packed ring isn't enabled on remoteproc for now,
+	 * because remoteproc uses vring_new_virtqueue() which
+	 * creates virtio rings on preallocated memory.
+	 */
+	__virtio_clear_bit(vdev, VIRTIO_F_RING_PACKED);
+}
+
 static int rproc_virtio_finalize_features(struct virtio_device *vdev)
 {
 	struct rproc_vdev *rvdev = vdev_to_rvdev(vdev);
@@ -224,6 +234,9 @@ static int rproc_virtio_finalize_features(struct virtio_device *vdev)
 	/* Give virtio_ring a chance to accept features */
 	vring_transport_features(vdev);
 
+	/* Give virtio_rproc a chance to accept features. */
+	rproc_transport_features(vdev);
+
 	/* Make sure we don't have any features > 32 bits! */
 	BUG_ON((u32)vdev->features != vdev->features);