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virtio-net: avoid sg copy

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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 <mst@redhat.com>
This commit is contained in:
Michael S. Tsirkin 2012-09-24 13:14:16 +02:00
parent d336336c81
commit 22cc84db6e
1 changed files with 23 additions and 25 deletions
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48
hw/virtio-net.c
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@ -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;