From 22cc84db6e42bef8646b8cd671f4c999e9c0a38f Mon Sep 17 00:00:00 2001 From: "Michael S. Tsirkin" Date: Mon, 24 Sep 2012 13:14:16 +0200 Subject: virtio-net: avoid sg copy Avoid tweaking iovec during receive. This removes the need to copy the vector. Note: we currently have an evil cast in work_around_broken_dhclient and unfortunately this patch does not fix it - just pushes the evil cast to another place. Signed-off-by: Michael S. Tsirkin --- hw/virtio-net.c | 48 +++++++++++++++++++++++------------------------- 1 file changed, 23 insertions(+), 25 deletions(-) (limited to 'hw/virtio-net.c') diff --git a/hw/virtio-net.c b/hw/virtio-net.c index a0c79e1d1b..84615869cb 100644 --- a/hw/virtio-net.c +++ b/hw/virtio-net.c @@ -504,40 +504,37 @@ static int virtio_net_has_buffers(VirtIONet *n, int bufsize) * cache. */ static void work_around_broken_dhclient(struct virtio_net_hdr *hdr, - const uint8_t *buf, size_t size) + uint8_t *buf, size_t size) { if ((hdr->flags & VIRTIO_NET_HDR_F_NEEDS_CSUM) && /* missing csum */ (size > 27 && size < 1500) && /* normal sized MTU */ (buf[12] == 0x08 && buf[13] == 0x00) && /* ethertype == IPv4 */ (buf[23] == 17) && /* ip.protocol == UDP */ (buf[34] == 0 && buf[35] == 67)) { /* udp.srcport == bootps */ - /* FIXME this cast is evil */ - net_checksum_calculate((uint8_t *)buf, size); + net_checksum_calculate(buf, size); 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); + /* FIXME this cast is evil */ + void *wbuf = (void *)buf; + work_around_broken_dhclient(wbuf, wbuf + 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 +595,8 @@ 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 +613,7 @@ 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 +638,20 @@ 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; -- cgit v1.2.1