From patchwork Mon Sep 24 23:04:40 2012 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Michael S. Tsirkin" X-Patchwork-Id: 186598 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Received: from lists.gnu.org (lists.gnu.org [208.118.235.17]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (Client did not present a certificate) by ozlabs.org (Postfix) with ESMTPS id F22B42C0080 for ; Tue, 25 Sep 2012 09:03:49 +1000 (EST) Received: from localhost ([::1]:33651 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TGHgq-0006Du-3p for incoming@patchwork.ozlabs.org; Mon, 24 Sep 2012 19:03:48 -0400 Received: from eggs.gnu.org ([208.118.235.92]:39529) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TGHgW-0006BE-Us for qemu-devel@nongnu.org; Mon, 24 Sep 2012 19:03:30 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1TGHgV-0005Xl-OZ for qemu-devel@nongnu.org; Mon, 24 Sep 2012 19:03:28 -0400 Received: from mx1.redhat.com ([209.132.183.28]:47735) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TGHgV-0005Xc-GH for qemu-devel@nongnu.org; Mon, 24 Sep 2012 19:03:27 -0400 Received: from int-mx10.intmail.prod.int.phx2.redhat.com (int-mx10.intmail.prod.int.phx2.redhat.com [10.5.11.23]) by mx1.redhat.com (8.14.4/8.14.4) with ESMTP id q8ON360J032476 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK); Mon, 24 Sep 2012 19:03:06 -0400 Received: from redhat.com (vpn1-7-132.ams2.redhat.com [10.36.7.132]) by int-mx10.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with SMTP id q8ON34sO012025; Mon, 24 Sep 2012 19:03:04 -0400 Date: Tue, 25 Sep 2012 01:04:40 +0200 From: "Michael S. Tsirkin" To: qemu-devel@nongnu.org, Jason Wang , Anthony Liguori , stefanha@linux.vnet.ibm.com, aurelien@aurel32.net Message-ID: <04d3e68d5be34a87514a33fcd789339748d43cb5.1348527749.git.mst@redhat.com> References: MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: X-Mutt-Fcc: =sent X-Scanned-By: MIMEDefang 2.68 on 10.5.11.23 X-detected-operating-system: by eggs.gnu.org: Genre and OS details not recognized. X-Received-From: 209.132.183.28 Subject: [Qemu-devel] [PATCH 04/14] virtio-net: avoid sg copy X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Sender: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Avoid tweaking iovec during receive. This removes the need to copy the vector. Note: we already have an evil cast in work_around_broken_dhclient and unfortunately this adds another one. const on buf is ignored by this function anyway so arguably this is not making things much worse. Signed-off-by: Michael S. Tsirkin --- hw/virtio-net.c | 45 +++++++++++++++++++++------------------------ iov.h | 8 ++++---- 2 files changed, 25 insertions(+), 28 deletions(-) diff --git a/hw/virtio-net.c b/hw/virtio-net.c index 0c5081e..6e53858 100644 --- a/hw/virtio-net.c +++ b/hw/virtio-net.c @@ -503,7 +503,7 @@ static int virtio_net_has_buffers(VirtIONet *n, int bufsize) * we should provide a mechanism to disable it to avoid polluting the host * cache. */ -static void work_around_broken_dhclient(struct virtio_net_hdr *hdr, +static void work_around_broken_dhclient(const struct virtio_net_hdr *hdr, const uint8_t *buf, size_t size) { if ((hdr->flags & VIRTIO_NET_HDR_F_NEEDS_CSUM) && /* missing csum */ @@ -513,31 +513,27 @@ static void work_around_broken_dhclient(struct virtio_net_hdr *hdr, (buf[34] == 0 && buf[35] == 67)) { /* udp.srcport == bootps */ /* FIXME this cast is evil */ net_checksum_calculate((uint8_t *)buf, size); - hdr->flags &= ~VIRTIO_NET_HDR_F_NEEDS_CSUM; + ((struct virtio_net_hdr *)hdr)->flags &= ~VIRTIO_NET_HDR_F_NEEDS_CSUM; } } -static int receive_header(VirtIONet *n, struct iovec *iov, int iovcnt, - const void *buf, size_t size, size_t hdr_len) +static int receive_header(VirtIONet *n, const struct iovec *iov, int iov_cnt, + const void *buf, size_t size) { - struct virtio_net_hdr *hdr = (struct virtio_net_hdr *)iov[0].iov_base; int offset = 0; - hdr->flags = 0; - hdr->gso_type = VIRTIO_NET_HDR_GSO_NONE; - if (n->has_vnet_hdr) { - memcpy(hdr, buf, sizeof(*hdr)); - offset = sizeof(*hdr); - work_around_broken_dhclient(hdr, buf + offset, size - offset); + work_around_broken_dhclient(buf, buf + offset, size - offset); + offset = sizeof(struct virtio_net_hdr); + iov_from_buf(iov, iov_cnt, 0, buf, offset); + } else { + struct virtio_net_hdr hdr = { + .flags = 0, + .gso_type = VIRTIO_NET_HDR_GSO_NONE + }; + iov_from_buf(iov, iov_cnt, 0, &hdr, sizeof hdr); } - /* We only ever receive a struct virtio_net_hdr from the tapfd, - * but we may be passing along a larger header to the guest. - */ - iov[0].iov_base += hdr_len; - iov[0].iov_len -= hdr_len; - return offset; } @@ -598,7 +594,8 @@ static ssize_t virtio_net_receive(NetClientState *nc, const uint8_t *buf, size_t { VirtIONet *n = DO_UPCAST(NICState, nc, nc)->opaque; struct virtio_net_hdr_mrg_rxbuf *mhdr = NULL; - size_t offset, i; + const struct iovec *sg = elem.in_sg; + size_t offset, i, guest_offset; if (!virtio_net_can_receive(&n->nic->nc)) return -1; @@ -615,7 +612,7 @@ static ssize_t virtio_net_receive(NetClientState *nc, const uint8_t *buf, size_t while (offset < size) { VirtQueueElement elem; int len, total; - struct iovec sg[VIRTQUEUE_MAX_SIZE]; + const struct iovec *sg = elem.in_sg; total = 0; @@ -640,20 +637,20 @@ static ssize_t virtio_net_receive(NetClientState *nc, const uint8_t *buf, size_t exit(1); } - memcpy(&sg, &elem.in_sg[0], sizeof(sg[0]) * elem.in_num); - if (i == 0) { if (n->mergeable_rx_bufs) mhdr = (struct virtio_net_hdr_mrg_rxbuf *)sg[0].iov_base; offset += receive_header(n, sg, elem.in_num, - buf + offset, size - offset, - n->guest_hdr_len); + buf + offset, size - offset); total += n->guest_hdr_len; + guest_offset = n->guest_hdr_len; + } else { + guest_offset = 0; } /* copy in packet. ugh */ - len = iov_from_buf(sg, elem.in_num, 0, + len = iov_from_buf(sg, elem.in_num, guest_offset, buf + offset, size - offset); total += len; offset += len; diff --git a/iov.h b/iov.h index f0daefa..6c9fdf1 100644 --- a/iov.h +++ b/iov.h @@ -90,8 +90,8 @@ void iov_hexdump(const struct iovec *iov, const unsigned int iov_cnt, /* * Partial copy of vector from iov to dst_iov (data is not copied). * dst_iov overlaps iov at a specified offset. - * size of dst_iov is at most bytes. Actual size is returned. + * size of dst_iov is at most bytes. dst vector count is returned. */ -size_t iov_cpy(struct iovec *dst_iov, unsigned int dst_iov_cnt, - const struct iovec *iov, unsigned int iov_cnt, - size_t offset, size_t bytes); +unsigned iov_cpy(struct iovec *dst_iov, unsigned int dst_iov_cnt, + const struct iovec *iov, unsigned int iov_cnt, + size_t offset, size_t bytes);