Re: [PATCH v6 24/46] virtio_net: get rid of virtio_net_hdr/skb_vnet_hdr

From: Jason Wang
Date: Fri Nov 28 2014 - 03:30:57 EST

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On Fri, Nov 28, 2014 at 4:09 AM, Michael S. Tsirkin <mst@xxxxxxxxxx> wrote:

virtio 1.0 doesn't use virtio_net_hdr anymore, and in fact, it's not
really useful since virtio_net_hdr_mrg_rxbuf includes that as the first
field anyway.

Let's drop it, precalculate header len and store within vi instead.

This way we can also remove struct skb_vnet_hdr.

Signed-off-by: Michael S. Tsirkin <mst@xxxxxxxxxx>
Reviewed-by: Cornelia Huck <cornelia.huck@xxxxxxxxxx>
---
drivers/net/virtio_net.c | 90 ++++++++++++++++++++++--------------------------
1 file changed, 41 insertions(+), 49 deletions(-)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 1630c21..516f2cb 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -123,6 +123,9 @@ struct virtnet_info {
/* Host can handle any s/g split between our header and packet data */
bool any_header_sg;
+ /* Packet virtio header size */
+ u8 hdr_len;
+
/* Active statistics */
struct virtnet_stats __percpu *stats;
@@ -139,21 +142,14 @@ struct virtnet_info {
struct notifier_block nb;
};
-struct skb_vnet_hdr {
- union {
- struct virtio_net_hdr hdr;
- struct virtio_net_hdr_mrg_rxbuf mhdr;
- };
-};
-
struct padded_vnet_hdr {
- struct virtio_net_hdr hdr;
+ struct virtio_net_hdr_mrg_rxbuf hdr;
/*
- * virtio_net_hdr should be in a separated sg buffer because of a
- * QEMU bug, and data sg buffer shares same page with this header sg.
- * This padding makes next sg 16 byte aligned after virtio_net_hdr.
+ * hdr is in a separate sg buffer, and data sg buffer shares same page
+ * with this header sg. This padding makes next sg 16 byte aligned
+ * after the header.
*/
- char padding[6];
+ char padding[4];
};
/* Converting between virtqueue no. and kernel tx/rx queue no.
@@ -179,9 +175,9 @@ static int rxq2vq(int rxq)
return rxq * 2;
}
-static inline struct skb_vnet_hdr *skb_vnet_hdr(struct sk_buff *skb)
+static inline struct virtio_net_hdr_mrg_rxbuf *skb_vnet_hdr(struct sk_buff *skb)
{
- return (struct skb_vnet_hdr *)skb->cb;
+ return (struct virtio_net_hdr_mrg_rxbuf *)skb->cb;
}
/*
@@ -247,7 +243,7 @@ static struct sk_buff *page_to_skb(struct virtnet_info *vi,
unsigned int len, unsigned int truesize)
{
struct sk_buff *skb;
- struct skb_vnet_hdr *hdr;
+ struct virtio_net_hdr_mrg_rxbuf *hdr;
unsigned int copy, hdr_len, hdr_padded_len;
char *p;
@@ -260,13 +256,11 @@ static struct sk_buff *page_to_skb(struct virtnet_info *vi,
hdr = skb_vnet_hdr(skb);
- if (vi->mergeable_rx_bufs) {
- hdr_len = sizeof hdr->mhdr;
- hdr_padded_len = sizeof hdr->mhdr;
- } else {
- hdr_len = sizeof hdr->hdr;
+ hdr_len = vi->hdr_len;
+ if (vi->mergeable_rx_bufs)
+ hdr_padded_len = sizeof *hdr;
+ else
hdr_padded_len = sizeof(struct padded_vnet_hdr);
- }
memcpy(hdr, p, hdr_len);
@@ -317,11 +311,11 @@ static struct sk_buff *page_to_skb(struct virtnet_info *vi,
return skb;
}
-static struct sk_buff *receive_small(void *buf, unsigned int len)
+static struct sk_buff *receive_small(struct virtnet_info *vi, void *buf, unsigned int len)
{
struct sk_buff * skb = buf;
- len -= sizeof(struct virtio_net_hdr);
+ len -= vi->hdr_len;
skb_trim(skb, len);
return skb;
@@ -354,8 +348,8 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
unsigned int len)
{
void *buf = mergeable_ctx_to_buf_address(ctx);
- struct skb_vnet_hdr *hdr = buf;
- u16 num_buf = virtio16_to_cpu(rq->vq->vdev, hdr->mhdr.num_buffers);
+ struct virtio_net_hdr_mrg_rxbuf *hdr = buf;
+ u16 num_buf = virtio16_to_cpu(vi->vdev, hdr->num_buffers);
struct page *page = virt_to_head_page(buf);
int offset = buf - page_address(page);
unsigned int truesize = max(len, mergeable_ctx_to_buf_truesize(ctx));
@@ -373,8 +367,8 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
if (unlikely(!ctx)) {
pr_debug("%s: rx error: %d buffers out of %d missing\n",
dev->name, num_buf,
- virtio16_to_cpu(rq->vq->vdev,
- hdr->mhdr.num_buffers));
+ virtio16_to_cpu(vi->vdev,
+ hdr->num_buffers));
dev->stats.rx_length_errors++;
goto err_buf;
}
@@ -441,7 +435,7 @@ static void receive_buf(struct virtnet_info *vi, struct receive_queue *rq,
struct net_device *dev = vi->dev;
struct virtnet_stats *stats = this_cpu_ptr(vi->stats);
struct sk_buff *skb;
- struct skb_vnet_hdr *hdr;
+ struct virtio_net_hdr_mrg_rxbuf *hdr;
if (unlikely(len < sizeof(struct virtio_net_hdr) + ETH_HLEN)) {
pr_debug("%s: short packet %i\n", dev->name, len);
@@ -463,7 +457,7 @@ static void receive_buf(struct virtnet_info *vi, struct receive_queue *rq,
else if (vi->big_packets)
skb = receive_big(dev, vi, rq, buf, len);
else
- skb = receive_small(buf, len);
+ skb = receive_small(vi, buf, len);
if (unlikely(!skb))
return;
@@ -545,7 +539,7 @@ static int add_recvbuf_small(struct virtnet_info *vi, struct receive_queue *rq,
gfp_t gfp)
{
struct sk_buff *skb;
- struct skb_vnet_hdr *hdr;
+ struct virtio_net_hdr_mrg_rxbuf *hdr;
int err;
skb = __netdev_alloc_skb_ip_align(vi->dev, GOOD_PACKET_LEN, gfp);
@@ -556,7 +550,7 @@ static int add_recvbuf_small(struct virtnet_info *vi, struct receive_queue *rq,
hdr = skb_vnet_hdr(skb);
sg_init_table(rq->sg, MAX_SKB_FRAGS + 2);
- sg_set_buf(rq->sg, &hdr->hdr, sizeof hdr->hdr);
+ sg_set_buf(rq->sg, hdr, vi->hdr_len);
skb_to_sgvec(skb, rq->sg + 1, 0, skb->len);
err = virtqueue_add_inbuf(rq->vq, rq->sg, 2, skb, gfp);
@@ -566,7 +560,8 @@ static int add_recvbuf_small(struct virtnet_info *vi, struct receive_queue *rq,
return err;
}
-static int add_recvbuf_big(struct receive_queue *rq, gfp_t gfp)
+static int add_recvbuf_big(struct virtnet_info *vi, struct receive_queue *rq,
+ gfp_t gfp)
{
struct page *first, *list = NULL;
char *p;
@@ -597,8 +592,8 @@ static int add_recvbuf_big(struct receive_queue *rq, gfp_t gfp)
p = page_address(first);
/* rq->sg[0], rq->sg[1] share the same page */
- /* a separated rq->sg[0] for virtio_net_hdr only due to QEMU bug */
- sg_set_buf(&rq->sg[0], p, sizeof(struct virtio_net_hdr));
+ /* a separated rq->sg[0] for header - required in case !any_header_sg */
+ sg_set_buf(&rq->sg[0], p, vi->hdr_len);
/* rq->sg[1] for data packet, from offset */
offset = sizeof(struct padded_vnet_hdr);
@@ -677,7 +672,7 @@ static bool try_fill_recv(struct virtnet_info *vi, struct receive_queue *rq,
if (vi->mergeable_rx_bufs)
err = add_recvbuf_mergeable(rq, gfp);
else if (vi->big_packets)
- err = add_recvbuf_big(rq, gfp);
+ err = add_recvbuf_big(vi, rq, gfp);
else
err = add_recvbuf_small(vi, rq, gfp);
@@ -857,18 +852,14 @@ static void free_old_xmit_skbs(struct send_queue *sq)
static int xmit_skb(struct send_queue *sq, struct sk_buff *skb)
{
- struct skb_vnet_hdr *hdr;
+ struct virtio_net_hdr_mrg_rxbuf *hdr;
const unsigned char *dest = ((struct ethhdr *)skb->data)->h_dest;
struct virtnet_info *vi = sq->vq->vdev->priv;
unsigned num_sg;
- unsigned hdr_len;
+ unsigned hdr_len = vi->hdr_len;
bool can_push;
pr_debug("%s: xmit %p %pM\n", vi->dev->name, skb, dest);
- if (vi->mergeable_rx_bufs)
- hdr_len = sizeof hdr->mhdr;
- else
- hdr_len = sizeof hdr->hdr;
can_push = vi->any_header_sg &&
!((unsigned long)skb->data & (__alignof__(*hdr) - 1)) &&
@@ -876,7 +867,7 @@ static int xmit_skb(struct send_queue *sq, struct sk_buff *skb)
/* Even if we can, don't push here yet as this would skew
* csum_start offset below. */
if (can_push)
- hdr = (struct skb_vnet_hdr *)(skb->data - hdr_len);
+ hdr = (struct virtio_net_hdr_mrg_rxbuf *)(skb->data - hdr_len);
else
hdr = skb_vnet_hdr(skb);
@@ -909,7 +900,7 @@ static int xmit_skb(struct send_queue *sq, struct sk_buff *skb)
}
if (vi->mergeable_rx_bufs)
- hdr->mhdr.num_buffers = 0;
+ hdr->num_buffers = 0;
sg_init_table(sq->sg, MAX_SKB_FRAGS + 2);
if (can_push) {
@@ -1814,18 +1805,19 @@ static int virtnet_probe(struct virtio_device *vdev)
if (virtio_has_feature(vdev, VIRTIO_NET_F_MRG_RXBUF))
vi->mergeable_rx_bufs = true;
+ if (virtio_has_feature(vdev, VIRTIO_NET_F_MRG_RXBUF))
+ vi->hdr_len = sizeof(struct virtio_net_hdr_mrg_rxbuf);
+ else
+ vi->hdr_len = sizeof(struct virtio_net_hdr);
+
if (virtio_has_feature(vdev, VIRTIO_F_ANY_LAYOUT))
vi->any_header_sg = true;
if (virtio_has_feature(vdev, VIRTIO_NET_F_CTRL_VQ))
vi->has_cvq = true;
- if (vi->any_header_sg) {
- if (vi->mergeable_rx_bufs)
- dev->needed_headroom = sizeof(struct virtio_net_hdr_mrg_rxbuf);
- else
- dev->needed_headroom = sizeof(struct virtio_net_hdr);
- }
+ if (vi->any_header_sg)
+ dev->needed_headroom = vi->hdr_len;
/* Use single tx/rx queue pair as default */
vi->curr_queue_pairs = 1;
--
MST

Reviewed-by: Jason Wang <jasowang@xxxxxxxxxx>

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Next message: Jason Wang: "Re: [PATCH v6 25/46] virtio_net: stricter short buffer length checks"
Previous message: Alexander Stein: "Re: Re: [PATCH 00/11] ARM: at91: remove !DT support for at91rm9200"
In reply to: Michael S. Tsirkin: "[PATCH v6 24/46] virtio_net: get rid of virtio_net_hdr/skb_vnet_hdr"
Next in thread: Michael S. Tsirkin: "[PATCH v6 26/46] virtio_net: bigger header when VERSION_1 is set"
Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]