virtio: endianness checks for virtio 1.0 devices

Add code that checks for the VERSION_1 feature bit in order to make
decisions about the device's endianness. This allows us to support
transitional devices.
Signed-off-by: NCornelia Huck <cornelia.huck@de.ibm.com>
Reviewed-by: NMichael S. Tsirkin <mst@redhat.com>
Signed-off-by: NMichael S. Tsirkin <mst@redhat.com>
Reviewed-by: NMichael S. Tsirkin <mst@redhat.com>

hw/virtio/virtio.c

@@ -903,7 +903,11 @@ static bool virtio_device_endian_needed(void *opaque)
     VirtIODevice *vdev = opaque;
 
     assert(vdev->device_endian != VIRTIO_DEVICE_ENDIAN_UNKNOWN);
+    if (!virtio_has_feature(vdev, VIRTIO_F_VERSION_1)) {
         return vdev->device_endian != virtio_default_endian();
+    }
+    /* Devices conforming to VIRTIO 1.0 or later are always LE. */
+    return vdev->device_endian != VIRTIO_DEVICE_ENDIAN_LITTLE;
 }
 
 static bool virtio_64bit_features_needed(void *opaque)

include/hw/virtio/virtio-access.h

@@ -19,6 +19,10 @@
 
 static inline bool virtio_access_is_big_endian(VirtIODevice *vdev)
 {
+    if (virtio_has_feature(vdev, VIRTIO_F_VERSION_1)) {
+        /* Devices conforming to VIRTIO 1.0 or later are always LE. */
+        return false;
+    }
 #if defined(TARGET_IS_BIENDIAN)
     return virtio_is_big_endian(vdev);
 #elif defined(TARGET_WORDS_BIGENDIAN)

include/hw/virtio/virtio.h

@@ -252,7 +252,11 @@ static inline bool virtio_has_feature(VirtIODevice *vdev, unsigned int fbit)
 
 static inline bool virtio_is_big_endian(VirtIODevice *vdev)
 {
+    if (!virtio_has_feature(vdev, VIRTIO_F_VERSION_1)) {
         assert(vdev->device_endian != VIRTIO_DEVICE_ENDIAN_UNKNOWN);
         return vdev->device_endian == VIRTIO_DEVICE_ENDIAN_BIG;
+    }
+    /* Devices conforming to VIRTIO 1.0 or later are always LE. */
+    return false;
 }
 #endif