From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:54591) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1aWfzJ-0007Vf-US for qemu-devel@nongnu.org; Fri, 19 Feb 2016 03:00:34 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1aWfzI-0001xL-Uu for qemu-devel@nongnu.org; Fri, 19 Feb 2016 03:00:29 -0500 Received: from mx1.redhat.com ([209.132.183.28]:39664) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1aWfzI-0001x9-PP for qemu-devel@nongnu.org; Fri, 19 Feb 2016 03:00:28 -0500 Date: Fri, 19 Feb 2016 10:00:25 +0200 From: "Michael S. Tsirkin" Message-ID: <1455868726-26350-7-git-send-email-mst@redhat.com> References: <1455868726-26350-1-git-send-email-mst@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1455868726-26350-1-git-send-email-mst@redhat.com> Subject: [Qemu-devel] [PULL 06/13] virtio: optimize virtio_access_is_big_endian() for little-endian targets List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: Cornelia Huck , Peter Maydell , Laurent Vivier , Greg Kurz From: Greg Kurz 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 Reviewed-by: Laurent Vivier Signed-off-by: Greg Kurz Reviewed-by: Michael S. Tsirkin Signed-off-by: Michael S. Tsirkin Reviewed-by: Laurent Vivier --- 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