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Re: [Qemu-devel] [PATCH v2 5/5] virtio: optimize virtio_access_is_big_en
From: |
Cornelia Huck |
Subject: |
Re: [Qemu-devel] [PATCH v2 5/5] virtio: optimize virtio_access_is_big_endian() for little-endian targets |
Date: |
Mon, 11 Jan 2016 19:18:52 +0100 |
On Mon, 11 Jan 2016 17:18:06 +0100
Greg Kurz <address@hidden> wrote:
> 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.
>
> Signed-off-by: Greg Kurz <address@hidden>
> ---
> v2:
> - simplified the logic as suggested by Laurent Vivier
> ---
> include/hw/virtio/virtio-access.h | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
Reviewed-by: Cornelia Huck <address@hidden>
- Re: [Qemu-devel] [PATCH v2 1/5] virtio-net: use the backend cross-endian capabilities, (continued)
[Qemu-devel] [PATCH v2 2/5] Revert "vhost-net: tell tap backend about the vnet endianness", Greg Kurz, 2016/01/11
[Qemu-devel] [PATCH v2 3/5] virtio: move cross-endian helper to vhost, Greg Kurz, 2016/01/11
[Qemu-devel] [PATCH v2 4/5] vhost: move virtio 1.0 check to cross-endian helper, Greg Kurz, 2016/01/11
[Qemu-devel] [PATCH v2 5/5] virtio: optimize virtio_access_is_big_endian() for little-endian targets, Greg Kurz, 2016/01/11