From: Pierrick Bouvier <[email protected]>
Thanks to previous refactoring, we can see more easily it is strictly
equivalent to always call virtio_vdev_is_big_endian.
static inline bool virtio_vdev_is_big_endian(VirtIODevice *vdev)
{
if (virtio_vdev_is_legacy(vdev)) {
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;
}
The key is to understand that vdev->device_endian is initialized as
expected. It always contains cpu endianness, and not
device endianness, ignoring if device is legacy or not.
By default, it's initialized to vdev->device_endian =
virtio_default_endian(), which matches target default endianness.
Then, on virtio_reset, it will be initialized with current_cpu
endianness (if there is one current_cpu).
void virtio_reset() {
...
if (current_cpu) {
/* Guest initiated reset */
vdev->device_endian = virtio_current_cpu_endian();
} else {
/* System reset */
vdev->device_endian = virtio_default_endian();
}
Now, we can see how existing virtio_access_is_big_endian is equivalent
to virtio_vdev_is_big_endian. Let's break the existing function in its 3
variants, and compare that to virtio_vdev_is_big_endian.
static inline bool virtio_access_is_big_endian(VirtIODevice *vdev)
- #if defined(LEGACY_VIRTIO_IS_BIENDIAN)
return virtio_vdev_is_big_endian(vdev);
This is the exact replacement we did, so equivalent.
- #elif TARGET_BIG_ENDIAN
if (!virtio_vdev_is_legacy(vdev)) {
return false;
}
return true;
we know target_is_big_endian(), so
vdev->device_endian == VIRTIO_DEVICE_ENDIAN_BIG.
if (virtio_vdev_is_legacy(vdev)) {
return VIRTIO_DEVICE_ENDIAN_BIG == VIRTIO_DEVICE_ENDIAN_BIG;
}
return false;
It's written in opposite style compared to existing code (if legacy vs
if modern), but it's strictly equivalent.
- #else
return false;
we know !target_is_big_endian(), so
vdev->device_endian == VIRTIO_DEVICE_ENDIAN_LITTLE.
if virtio_vdev_is_legacy(vdev) {
return VIRTIO_DEVICE_ENDIAN_LITTLE == VIRTIO_DEVICE_ENDIAN_BIG;
}
return false;
So it always return false, as expected.
Signed-off-by: Pierrick Bouvier <[email protected]>
Reviewed-by: Philippe Mathieu-Daudé <[email protected]>
Acked-by: Stefan Hajnoczi <[email protected]>
Signed-off-by: Philippe Mathieu-Daudé <[email protected]>
---
include/hw/virtio/virtio-access.h | 14 --------------
1 file changed, 14 deletions(-)
diff --git a/include/hw/virtio/virtio-access.h
b/include/hw/virtio/virtio-access.h
index b8aa7a520f5..e3148c23881 100644
--- a/include/hw/virtio/virtio-access.h
+++ b/include/hw/virtio/virtio-access.h
@@ -21,23 +21,9 @@
#include "hw/virtio/virtio.h"
#include "hw/virtio/virtio-bus.h"
-#if defined(TARGET_PPC64) || defined(TARGET_ARM)
-#define LEGACY_VIRTIO_IS_BIENDIAN 1
-#endif
-
static inline bool virtio_access_is_big_endian(VirtIODevice *vdev)
{
-#if defined(LEGACY_VIRTIO_IS_BIENDIAN)
return virtio_vdev_is_big_endian(vdev);
-#elif TARGET_BIG_ENDIAN
- if (!virtio_vdev_is_legacy(vdev)) {
- /* Devices conforming to VIRTIO 1.0 or later are always LE. */
- return false;
- }
- return true;
-#else
- return false;
-#endif
}
static inline void virtio_stw_p(VirtIODevice *vdev, void *ptr, uint16_t v)
--
2.52.0
