On Thu, 2008-10-09 at 23:30 +0800, Herbert Xu wrote:
> On Thu, Oct 09, 2008 at 11:55:59AM +1100, Rusty Russell wrote:
> > > The size of the logical buffer is
> > > returned to the guest rather than the size of the individual smaller
> > > buffers.
> >
> > That's a virtio transport breakage: can you use the standard virtio
> > mechanism,
> > just put the extended length or number of extra buffers inside the
> > virtio_net_hdr?
>
> Sure that sounds reasonable.
Okay, here we go.
The new header is lamely called virtio_net_hdr2 - I've added some
padding in there so we can extend it further in future.
It gets messy for lguest because tun/tap isn't using the same header
format anymore.
Rusty - let me know if this looks reasonable and, if so, I'll merge it
back into the original patches and resend.
Cheers,
Mark.
diff --git a/Documentation/lguest/lguest.c b/Documentation/lguest/lguest.c
index da934c2..0f840f2 100644
--- a/Documentation/lguest/lguest.c
+++ b/Documentation/lguest/lguest.c
@@ -940,14 +940,21 @@ static void handle_net_output(int fd, struct virtqueue
*vq, bool timeout)
{
unsigned int head, out, in, num = 0;
int len;
- struct iovec iov[vq->vring.num];
+ struct iovec iov[vq->vring.num + 1];
static int last_timeout_num;
/* Keep getting output buffers from the Guest until we run out. */
- while ((head = get_vq_desc(vq, iov, &out, &in)) != vq->vring.num) {
+ while ((head = get_vq_desc(vq, &iov[1], &out, &in)) != vq->vring.num) {
if (in)
errx(1, "Input buffers in output queue?");
- len = writev(vq->dev->fd, iov, out);
+
+ /* tapfd needs a virtio_net_hdr, not virtio_net_hdr2 */
+ iov[0].iov_base = iov[1].iov_base;
+ iov[0].iov_len = sizeof(struct virtio_net_hdr);
+ iov[1].iov_base += sizeof(struct virtio_net_hdr2);
+ iov[1].iov_len -= sizeof(struct virtio_net_hdr2);
+
+ len = writev(vq->dev->fd, iov, out + 1);
if (len < 0)
err(1, "Writing network packet to tun");
add_used_and_trigger(fd, vq, head, len);
@@ -998,18 +1005,24 @@ static unsigned int get_net_recv_head(struct device
*dev, struct iovec *iov,
/* Here we add used recv buffers to the used queue but, also, return unused
* buffers to the avail queue. */
-static void add_net_recv_used(struct device *dev, unsigned int *heads,
- int *bufsizes, int nheads, int used_len)
+static void add_net_recv_used(struct device *dev, struct virtio_net_hdr2 *hdr2,
+ unsigned int *heads, int *bufsizes,
+ int nheads, int used_len)
{
int len, idx;
/* Add the buffers we've actually used to the used queue */
len = idx = 0;
while (len < used_len) {
- add_used(dev->vq, heads[idx], used_len, idx);
+ if (bufsizes[idx] > (used_len - len))
+ bufsizes[idx] = used_len - len;
+ add_used(dev->vq, heads[idx], bufsizes[idx], idx);
len += bufsizes[idx++];
}
+ /* The guest needs to know how many buffers to fetch */
+ hdr2->num_buffers = idx;
+
/* Return the rest of them back to the avail queue */
lg_last_avail(dev->vq) -= nheads - idx;
dev->vq->inflight -= nheads - idx;
@@ -1022,12 +1035,17 @@ static void add_net_recv_used(struct device *dev,
unsigned int *heads,
* Guest. */
static bool handle_tun_input(int fd, struct device *dev)
{
- struct iovec iov[dev->vq->vring.num];
+ struct virtio_net_hdr hdr;
+ struct virtio_net_hdr2 *hdr2;
+ struct iovec iov[dev->vq->vring.num + 1];
unsigned int heads[NET_MAX_RECV_PAGES];
int bufsizes[NET_MAX_RECV_PAGES];
int nheads, len, iovcnt;
- nheads = len = iovcnt = 0;
+ nheads = len = 0;
+
+ /* First iov is for the header */
+ iovcnt = 1;
/* First we need enough network buffers from the Guests's recv
* virtqueue for the largest possible packet. */
@@ -1056,13 +1074,26 @@ static bool handle_tun_input(int fd, struct device *dev)
len += bufsizes[nheads++];
}
+ /* Read virtio_net_hdr from tapfd */
+ iov[0].iov_base = &hdr;
+ iov[0].iov_len = sizeof(hdr);
+
+ /* Read data into buffer after virtio_net_hdr2 */
+ hdr2 = iov[1].iov_base;
+ iov[1].iov_base += sizeof(*hdr2);
+ iov[1].iov_len -= sizeof(*hdr2);
+
/* Read the packet from the device directly into the Guest's buffer. */
len = readv(dev->fd, iov, iovcnt);
if (len <= 0)
err(1, "reading network");
+ /* Copy the virtio_net_hdr into the virtio_net_hdr2 */
+ hdr2->hdr = hdr;
+ len += sizeof(*hdr2) - sizeof(hdr);
+
/* Return unused buffers to the recv queue */
- add_net_recv_used(dev, heads, bufsizes, nheads, len);
+ add_net_recv_used(dev, hdr2, heads, bufsizes, nheads, len);
/* Fire in the hole ! */
trigger_irq(fd, dev->vq);
diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 1780d6d..719e9dc 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -61,6 +61,7 @@ struct virtnet_info
/* Host will merge rx buffers for big packets (shake it! shake it!) */
bool mergeable_rx_bufs;
+ bool use_vnet_hdr2;
/* Receive & send queues. */
struct sk_buff_head recv;
@@ -70,11 +71,21 @@ struct virtnet_info
struct page *pages;
};
+static inline struct virtio_net_hdr2 *skb_vnet_hdr2(struct sk_buff *skb)
+{
+ return (struct virtio_net_hdr2 *)skb->cb;
+}
+
static inline struct virtio_net_hdr *skb_vnet_hdr(struct sk_buff *skb)
{
return (struct virtio_net_hdr *)skb->cb;
}
+static inline void vnet_hdr2_to_sg(struct scatterlist *sg, struct sk_buff *skb)
+{
+ sg_init_one(sg, skb_vnet_hdr2(skb), sizeof(struct virtio_net_hdr2));
+}
+
static inline void vnet_hdr_to_sg(struct scatterlist *sg, struct sk_buff *skb)
{
sg_init_one(sg, skb_vnet_hdr(skb), sizeof(struct virtio_net_hdr));
@@ -135,43 +146,40 @@ static void receive_skb(struct net_device *dev, struct
sk_buff *skb,
dev->stats.rx_length_errors++;
goto drop;
}
- len -= sizeof(struct virtio_net_hdr);
if (vi->mergeable_rx_bufs) {
+ struct virtio_net_hdr2 *hdr2 = skb_vnet_hdr2(skb);
unsigned int copy;
- unsigned int plen;
char *p = page_address(skb_shinfo(skb)->frags[0].page);
- memcpy(hdr, p, sizeof(*hdr));
- p += sizeof(*hdr);
+ if (len > PAGE_SIZE)
+ len = PAGE_SIZE;
+ len -= sizeof(struct virtio_net_hdr2);
- plen = PAGE_SIZE - sizeof(*hdr);
- if (plen > len)
- plen = len;
+ memcpy(hdr2, p, sizeof(*hdr2));
+ p += sizeof(*hdr2);
- copy = plen;
+ copy = len;
if (copy > skb_tailroom(skb))
copy = skb_tailroom(skb);
memcpy(skb_put(skb, copy), p, copy);
len -= copy;
- plen -= copy;
- if (!plen) {
+ if (!len) {
give_a_page(vi, skb_shinfo(skb)->frags[0].page);
skb_shinfo(skb)->nr_frags--;
} else {
skb_shinfo(skb)->frags[0].page_offset +=
- sizeof(*hdr) + copy;
- skb_shinfo(skb)->frags[0].size = plen;
- skb->data_len += plen;
- skb->len += plen;
+ sizeof(*hdr2) + copy;
+ skb_shinfo(skb)->frags[0].size = len;
+ skb->data_len += len;
+ skb->len += len;
}
- while ((len -= plen)) {
+ while (--hdr2->num_buffers) {
struct sk_buff *nskb;
- unsigned nlen;
i = skb_shinfo(skb)->nr_frags;
if (i >= MAX_SKB_FRAGS) {
@@ -181,10 +189,10 @@ static void receive_skb(struct net_device *dev, struct
sk_buff *skb,
goto drop;
}
- nskb = vi->rvq->vq_ops->get_buf(vi->rvq, &nlen);
+ nskb = vi->rvq->vq_ops->get_buf(vi->rvq, &len);
if (!nskb) {
- pr_debug("%s: packet length error %d < %d\n",
- dev->name, skb->len, len);
+ pr_debug("%s: rx error: %d buffers missing\n",
+ dev->name, hdr2->num_buffers);
dev->stats.rx_length_errors++;
goto drop;
}
@@ -196,16 +204,17 @@ static void receive_skb(struct net_device *dev, struct
sk_buff *skb,
skb_shinfo(nskb)->nr_frags = 0;
kfree_skb(nskb);
- plen = PAGE_SIZE;
- if (plen > len)
- plen = len;
+ if (len > PAGE_SIZE)
+ len = PAGE_SIZE;
- skb_shinfo(skb)->frags[i].size = plen;
+ skb_shinfo(skb)->frags[i].size = len;
skb_shinfo(skb)->nr_frags++;
- skb->data_len += plen;
- skb->len += plen;
+ skb->data_len += len;
+ skb->len += len;
}
} else {
+ len -= sizeof(struct virtio_net_hdr);
+
if (len <= MAX_PACKET_LEN)
trim_pages(vi, skb);
@@ -451,6 +460,7 @@ static int xmit_skb(struct virtnet_info *vi, struct sk_buff
*skb)
{
int num, err;
struct scatterlist sg[2+MAX_SKB_FRAGS];
+ struct virtio_net_hdr2 *hdr2;
struct virtio_net_hdr *hdr;
const unsigned char *dest = ((struct ethhdr *)skb->data)->h_dest;
@@ -461,7 +471,9 @@ static int xmit_skb(struct virtnet_info *vi, struct sk_buff
*skb)
dest[3], dest[4], dest[5]);
/* Encode metadata header at front. */
- hdr = skb_vnet_hdr(skb);
+ hdr2 = skb_vnet_hdr2(skb);
+ hdr = &hdr2->hdr;
+
if (skb->ip_summed == CHECKSUM_PARTIAL) {
hdr->flags = VIRTIO_NET_HDR_F_NEEDS_CSUM;
hdr->csum_start = skb->csum_start - skb_headroom(skb);
@@ -489,7 +501,13 @@ static int xmit_skb(struct virtnet_info *vi, struct
sk_buff *skb)
hdr->gso_size = hdr->hdr_len = 0;
}
- vnet_hdr_to_sg(sg, skb);
+ hdr2->num_buffers = 0;
+
+ if (vi->use_vnet_hdr2)
+ vnet_hdr2_to_sg(sg, skb);
+ else
+ vnet_hdr_to_sg(sg, skb);
+
num = skb_to_sgvec(skb, sg+1, 0, skb->len) + 1;
err = vi->svq->vq_ops->add_buf(vi->svq, sg, num, 0, skb);
@@ -678,8 +696,10 @@ static int virtnet_probe(struct virtio_device *vdev)
|| virtio_has_feature(vdev, VIRTIO_NET_F_GUEST_ECN))
vi->big_packets = true;
- if (virtio_has_feature(vdev, VIRTIO_NET_F_MRG_RXBUF))
+ if (virtio_has_feature(vdev, VIRTIO_NET_F_MRG_RXBUF)) {
vi->mergeable_rx_bufs = true;
+ vi->use_vnet_hdr2 = true;
+ }
/* We expect two virtqueues, receive then send. */
vi->rvq = vdev->config->find_vq(vdev, 0, skb_recv_done);
diff --git a/include/linux/virtio_net.h b/include/linux/virtio_net.h
index 8f376a7..59a5079 100644
--- a/include/linux/virtio_net.h
+++ b/include/linux/virtio_net.h
@@ -45,4 +45,14 @@ struct virtio_net_hdr
__u16 csum_start; /* Position to start checksumming from */
__u16 csum_offset; /* Offset after that to place checksum */
};
+
+/* This is the version of the header to use when the MRG_RXBUF
+ * feature (or any later feature) has been negotiated. */
+struct virtio_net_hdr2
+{
+ struct virtio_net_hdr hdr;
+ __u8 num_buffers; /* Number of merged rx buffers */
+ __u8 pad[21]; /* Pad to 32 bytes */
+};
+
#endif /* _LINUX_VIRTIO_NET_H */
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