virtio: move cross-endian helper to vhost

If target is bi-endian (ppc64, arm), the virtio_legacy_is_cross_endian()
indeed returns the runtime state of the virtio device. However, it returns
false unconditionally in the general case. This sounds a bit strange
given the name of the function.

This helper is only useful for vhost actually, where indeed non bi-endian
targets don't have to deal with cross-endian issues.

This patch moves the helper to vhost.c and gives it a more appropriate name.
Reviewed-by: NCornelia Huck <cornelia.huck@de.ibm.com>
Reviewed-by: NLaurent Vivier <lvivier@redhat.com>
Signed-off-by: NGreg Kurz <gkurz@linux.vnet.ibm.com>
Reviewed-by: NMichael S. Tsirkin <mst@redhat.com>
Signed-off-by: NMichael S. Tsirkin <mst@redhat.com>
Reviewed-by: NLaurent Vivier <lvivier@redhat.com>

hw/virtio/vhost.c

@@ -749,6 +749,19 @@ static void vhost_log_stop(MemoryListener *listener,
     /* FIXME: implement */
 }
 
+static inline bool vhost_needs_vring_endian(VirtIODevice *vdev)
+{
+#ifdef TARGET_IS_BIENDIAN
+#ifdef HOST_WORDS_BIGENDIAN
+    return !virtio_is_big_endian(vdev);
+#else
+    return virtio_is_big_endian(vdev);
+#endif
+#else
+    return false;
+#endif
+}
+
 static int vhost_virtqueue_set_vring_endian_legacy(struct vhost_dev *dev,
                                                    bool is_big_endian,
                                                    int vhost_vq_index)
@@ -800,7 +813,7 @@ static int vhost_virtqueue_start(struct vhost_dev *dev,
     }
 
     if (!virtio_vdev_has_feature(vdev, VIRTIO_F_VERSION_1) &&
-        virtio_legacy_is_cross_endian(vdev)) {
+        vhost_needs_vring_endian(vdev)) {
         r = vhost_virtqueue_set_vring_endian_legacy(dev,
                                                     virtio_is_big_endian(vdev),
                                                     vhost_vq_index);
@@ -897,7 +910,7 @@ static void vhost_virtqueue_stop(struct vhost_dev *dev,
      * native as legacy devices expect so by default.
      */
     if (!virtio_vdev_has_feature(vdev, VIRTIO_F_VERSION_1) &&
-        virtio_legacy_is_cross_endian(vdev)) {
+        vhost_needs_vring_endian(vdev)) {
         r = vhost_virtqueue_set_vring_endian_legacy(dev,
                                                     !virtio_is_big_endian(vdev),
                                                     vhost_vq_index);

include/hw/virtio/virtio-access.h

@@ -32,19 +32,6 @@ static inline bool virtio_access_is_big_endian(VirtIODevice *vdev)
 #endif
 }
 
-static inline bool virtio_legacy_is_cross_endian(VirtIODevice *vdev)
-{
-#ifdef TARGET_IS_BIENDIAN
-#ifdef HOST_WORDS_BIGENDIAN
-    return !virtio_is_big_endian(vdev);
-#else
-    return virtio_is_big_endian(vdev);
-#endif
-#else
-    return false;
-#endif
-}
-
 static inline uint16_t virtio_lduw_phys(VirtIODevice *vdev, hwaddr pa)
 {
     if (virtio_access_is_big_endian(vdev)) {