virtio: add explicit big-endian support to memory accessors

The current memory accessors logic is:
- little endian if little_endian
- native endian (i.e. no byteswap) if !little_endian

If we want to fully support cross-endian vhost, we also need to be
able to convert to big endian.

Instead of changing the little_endian argument to some 3-value enum, this
patch changes the logic to:
- little endian if little_endian
- big endian if !little_endian

The native endian case is handled by all users with a trivial helper. This
patch doesn't change any functionality, nor it does add overhead.

Signed-off-by: Greg Kurz <gkurz@linux.vnet.ibm.com>

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>

1 files changed, 2 insertions, 1 deletions

diff --git a/include/linux/virtio_config.h b/include/linux/virtio_config.h
index 170947eb11b5..e5ce8ab0b8b0 100644
--- a/include/linux/virtio_config.h
+++ b/include/linux/virtio_config.h
@@ -207,7 +207,8 @@ int virtqueue_set_affinity(struct virtqueue *vq, int cpu)
 
 static inline bool virtio_is_little_endian(struct virtio_device *vdev)
 {
-	return virtio_has_feature(vdev, VIRTIO_F_VERSION_1);
+	return virtio_has_feature(vdev, VIRTIO_F_VERSION_1) ||
+		virtio_legacy_is_little_endian();
 }
 
 /* Memory accessors */