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[Qemu-devel] [PATCHv2 04/14] virtio-net: avoid sg copy
From: |
Michael S. Tsirkin |
Subject: |
[Qemu-devel] [PATCHv2 04/14] virtio-net: avoid sg copy |
Date: |
Tue, 25 Sep 2012 13:12:17 +0200 |
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 <address@hidden>
---
hw/virtio-net.c | 48 +++++++++++++++++++++++-------------------------
1 file changed, 23 insertions(+), 25 deletions(-)
diff --git a/hw/virtio-net.c b/hw/virtio-net.c
index 0c5081e..e2f354f 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;
--
MST
- [Qemu-devel] [PATCHv2 00/14] virtio-net: iovec handling cleanup, Michael S. Tsirkin, 2012/09/25
- [Qemu-devel] [PATCHv2 01/14] virtio-net: track host/guest header length, Michael S. Tsirkin, 2012/09/25
- [Qemu-devel] [PATCHv2 04/14] virtio-net: avoid sg copy,
Michael S. Tsirkin <=
- [Qemu-devel] [PATCHv2 02/14] iov: add const annotation, Michael S. Tsirkin, 2012/09/25
- [Qemu-devel] [PATCHv2 03/14] iov: add iov_cpy, Michael S. Tsirkin, 2012/09/25
- [Qemu-devel] [PATCHv2 06/14] virtio-net: refactor receive_hdr, Michael S. Tsirkin, 2012/09/25
- [Qemu-devel] [PATCHv2 05/14] virtio-net: use safe iov operations for rx, Michael S. Tsirkin, 2012/09/25
- [Qemu-devel] [PATCHv2 07/14] virtio-net: first s/g is always at start of buf, Michael S. Tsirkin, 2012/09/25
- [Qemu-devel] [PATCHv2 08/14] virtio-net: switch tx to safe iov functions, Michael S. Tsirkin, 2012/09/25
- [Qemu-devel] [PATCHv2 09/14] virtio-net: simplify rx code, Michael S. Tsirkin, 2012/09/25
- [Qemu-devel] [PATCHv2 12/14] virtio-net: minor code simplification, Michael S. Tsirkin, 2012/09/25
- [Qemu-devel] [PATCHv2 14/14] virtio-net: enable mrg buf header in tap on linux, Michael S. Tsirkin, 2012/09/25
- [Qemu-devel] [PATCHv2 10/14] virtio: don't mark unaccessed memory as dirty, Michael S. Tsirkin, 2012/09/25