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[Qemu-devel] [PULL 06/13] virtio: optimize virtio_access_is_big_endian()
From: |
Michael S. Tsirkin |
Subject: |
[Qemu-devel] [PULL 06/13] virtio: optimize virtio_access_is_big_endian() for little-endian targets |
Date: |
Fri, 19 Feb 2016 10:00:25 +0200 |
From: Greg Kurz <address@hidden>
When adding cross-endian support, we introduced the TARGET_IS_BIENDIAN macro
and the virtio_access_is_big_endian() helper to have a branchless fast path
in the virtio memory accessors for targets that don't switch endian.
This was considered as a strong requirement at the time.
Now we have added a runtime check for virtio 1.0, which ruins the benefit
of the virtio_access_is_big_endian() helper for always little-endian targets.
With this patch, always little-endian targets stop checking for virtio 1.0,
since the result is little-endian in all cases.
Reviewed-by: Cornelia Huck <address@hidden>
Reviewed-by: Laurent Vivier <address@hidden>
Signed-off-by: Greg Kurz <address@hidden>
Reviewed-by: Michael S. Tsirkin <address@hidden>
Signed-off-by: Michael S. Tsirkin <address@hidden>
Reviewed-by: Laurent Vivier <address@hidden>
---
include/hw/virtio/virtio-access.h | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/include/hw/virtio/virtio-access.h
b/include/hw/virtio/virtio-access.h
index f1f12af..8dc84f5 100644
--- a/include/hw/virtio/virtio-access.h
+++ b/include/hw/virtio/virtio-access.h
@@ -19,13 +19,13 @@
static inline bool virtio_access_is_big_endian(VirtIODevice *vdev)
{
+#if defined(TARGET_IS_BIENDIAN)
+ return virtio_is_big_endian(vdev);
+#elif defined(TARGET_WORDS_BIGENDIAN)
if (virtio_vdev_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)
return true;
#else
return false;
--
MST
- [Qemu-devel] [PULL 00/13] vhost, virtio, pci, pxe, Michael S. Tsirkin, 2016/02/19
- [Qemu-devel] [PULL 01/13] virtio-net: use the backend cross-endian capabilities, Michael S. Tsirkin, 2016/02/19
- [Qemu-devel] [PULL 02/13] vhost-net: revert support of cross-endian vnet headers, Michael S. Tsirkin, 2016/02/19
- [Qemu-devel] [PULL 03/13] virtio: move cross-endian helper to vhost, Michael S. Tsirkin, 2016/02/19
- [Qemu-devel] [PULL 05/13] vhost: simplify vhost_needs_vring_endian(), Michael S. Tsirkin, 2016/02/19
- [Qemu-devel] [PULL 04/13] vhost: move virtio 1.0 check to cross-endian helper, Michael S. Tsirkin, 2016/02/19
- [Qemu-devel] [PULL 06/13] virtio: optimize virtio_access_is_big_endian() for little-endian targets,
Michael S. Tsirkin <=
- [Qemu-devel] [PULL 07/13] msix: fix msix_vector_masked, Michael S. Tsirkin, 2016/02/19
- [Qemu-devel] [PULL 08/13] tests: add pxe e1000 and virtio-pci tests, Michael S. Tsirkin, 2016/02/19
- [Qemu-devel] [PULL 09/13] dec: convert to realize(), Michael S. Tsirkin, 2016/02/19
- [Qemu-devel] [PULL 10/13] change type of pci_bridge_initfn() to void, Michael S. Tsirkin, 2016/02/19
- [Qemu-devel] [PULL 11/13] rules: filter out irrelevant files, Michael S. Tsirkin, 2016/02/19
- [Qemu-devel] [PULL 12/13] vhost-user interrupt management fixes, Michael S. Tsirkin, 2016/02/19
- [Qemu-devel] [PULL 13/13] tests/vhost-user-bridge: add scattering of incoming packets, Michael S. Tsirkin, 2016/02/19