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Xuan Zhuo

2023-Mar-28 12:04 UTC

[PATCH net-next 7/8] virtio_net: introduce receive_mergeable_xdp()

The purpose of this patch is to simplify the receive_mergeable().
Separate all the logic of XDP into a function.

Signed-off-by: Xuan Zhuo <xuanzhuo at linux.alibaba.com>
---
 drivers/net/virtio_net.c | 128 +++++++++++++++++++++++----------------
 1 file changed, 76 insertions(+), 52 deletions(-)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 136131a7868a..c8978d8d8adb 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -1316,6 +1316,63 @@ static void *mergeable_xdp_prepare(struct virtnet_info
*vi,
 	return page_address(xdp_page) + VIRTIO_XDP_HEADROOM;
 }
 
+static struct sk_buff *receive_mergeable_xdp(struct net_device *dev,
+					     struct virtnet_info *vi,
+					     struct receive_queue *rq,
+					     struct bpf_prog *xdp_prog,
+					     void *buf,
+					     void *ctx,
+					     unsigned int len,
+					     unsigned int *xdp_xmit,
+					     struct virtnet_rq_stats *stats)
+{
+	struct virtio_net_hdr_mrg_rxbuf *hdr = buf;
+	int 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 xdp_frags_truesz = 0;
+	struct sk_buff *head_skb;
+	unsigned int frame_sz;
+	struct xdp_buff xdp;
+	void *data;
+	u32 act;
+	int err;
+
+	data = mergeable_xdp_prepare(vi, rq, xdp_prog, ctx, &frame_sz,
&num_buf, &page,
+				     offset, &len, hdr);
+	if (!data)
+		goto err_xdp;
+
+	err = virtnet_build_xdp_buff_mrg(dev, vi, rq, &xdp, data, len, frame_sz,
+					 &num_buf, &xdp_frags_truesz, stats);
+	if (unlikely(err))
+		goto err_xdp;
+
+	act = virtnet_xdp_handler(xdp_prog, &xdp, dev, xdp_xmit, stats);
+
+	switch (act) {
+	case VIRTNET_XDP_RES_PASS:
+		head_skb = build_skb_from_xdp_buff(dev, vi, &xdp, xdp_frags_truesz);
+		if (unlikely(!head_skb))
+			goto err_xdp;
+		return head_skb;
+
+	case VIRTNET_XDP_RES_CONSUMED:
+		return NULL;
+
+	case VIRTNET_XDP_RES_DROP:
+		break;
+	}
+
+err_xdp:
+	put_page(page);
+	mergeable_buf_free(rq, num_buf, dev, stats);
+
+	stats->xdp_drops++;
+	stats->drops++;
+	return NULL;
+}
+
 static struct sk_buff *receive_mergeable(struct net_device *dev,
 					 struct virtnet_info *vi,
 					 struct receive_queue *rq,
@@ -1325,21 +1382,22 @@ static struct sk_buff *receive_mergeable(struct
net_device *dev,
 					 unsigned int *xdp_xmit,
 					 struct virtnet_rq_stats *stats)
 {
-	struct virtio_net_hdr_mrg_rxbuf *hdr = buf;
-	int num_buf = virtio16_to_cpu(vi->vdev, hdr->num_buffers);
-	struct page *page = virt_to_head_page(buf);
-	int offset = buf - page_address(page);
-	struct sk_buff *head_skb, *curr_skb;
-	struct bpf_prog *xdp_prog;
 	unsigned int truesize = mergeable_ctx_to_truesize(ctx);
 	unsigned int headroom = mergeable_ctx_to_headroom(ctx);
 	unsigned int tailroom = headroom ? sizeof(struct skb_shared_info) : 0;
 	unsigned int room = SKB_DATA_ALIGN(headroom + tailroom);
-	unsigned int frame_sz;
-	int err;
+	struct virtio_net_hdr_mrg_rxbuf *hdr;
+	struct sk_buff *head_skb, *curr_skb;
+	struct bpf_prog *xdp_prog;
+	struct page *page;
+	int num_buf;
+	int offset;
 
 	head_skb = NULL;
 	stats->bytes += len - vi->hdr_len;
+	hdr = buf;
+	num_buf = virtio16_to_cpu(vi->vdev, hdr->num_buffers);
+	page = virt_to_head_page(buf);
 
 	if (unlikely(len > truesize - room)) {
 		pr_debug("%s: rx error: len %u exceeds truesize %lu\n",
@@ -1348,51 +1406,21 @@ static struct sk_buff *receive_mergeable(struct
net_device *dev,
 		goto err_skb;
 	}
 
-	if (likely(!vi->xdp_enabled)) {
-		xdp_prog = NULL;
-		goto skip_xdp;
-	}
-
-	rcu_read_lock();
-	xdp_prog = rcu_dereference(rq->xdp_prog);
-	if (xdp_prog) {
-		unsigned int xdp_frags_truesz = 0;
-		struct xdp_buff xdp;
-		void *data;
-		u32 act;
-
-		data = mergeable_xdp_prepare(vi, rq, xdp_prog, ctx, &frame_sz,
&num_buf, &page,
-					     offset, &len, hdr);
-		if (!data)
-			goto err_xdp;
-
-		err = virtnet_build_xdp_buff_mrg(dev, vi, rq, &xdp, data, len, frame_sz,
-						 &num_buf, &xdp_frags_truesz, stats);
-		if (unlikely(err))
-			goto err_xdp;
-
-		act = virtnet_xdp_handler(xdp_prog, &xdp, dev, xdp_xmit, stats);
-
-		switch (act) {
-		case VIRTNET_XDP_RES_PASS:
-			head_skb = build_skb_from_xdp_buff(dev, vi, &xdp, xdp_frags_truesz);
-			if (unlikely(!head_skb))
-				goto err_xdp;
-
+	if (likely(vi->xdp_enabled)) {
+		rcu_read_lock();
+		xdp_prog = rcu_dereference(rq->xdp_prog);
+		if (xdp_prog) {
+			head_skb = receive_mergeable_xdp(dev, vi, rq, xdp_prog,
+							 buf, ctx, len, xdp_xmit,
+							 stats);
 			rcu_read_unlock();
 			return head_skb;
-
-		case VIRTNET_XDP_RES_CONSUMED:
-			rcu_read_unlock();
-			goto xdp_xmit;
-
-		case VIRTNET_XDP_RES_DROP:
-			goto err_xdp;
 		}
+		rcu_read_unlock();
 	}
-	rcu_read_unlock();
 
-skip_xdp:
+	offset = buf - page_address(page);
+
 	head_skb = page_to_skb(vi, rq, page, offset, len, truesize, headroom);
 	curr_skb = head_skb;
 
@@ -1458,9 +1486,6 @@ static struct sk_buff *receive_mergeable(struct net_device
*dev,
 	ewma_pkt_len_add(&rq->mrg_avg_pkt_len, head_skb->len);
 	return head_skb;
 
-err_xdp:
-	rcu_read_unlock();
-	stats->xdp_drops++;
 err_skb:
 	put_page(page);
 	mergeable_buf_free(rq, num_buf, dev, stats);
@@ -1468,7 +1493,6 @@ static struct sk_buff *receive_mergeable(struct net_device
*dev,
 err_buf:
 	stats->drops++;
 	dev_kfree_skb(head_skb);
-xdp_xmit:
 	return NULL;
 }
 
-- 
2.32.0.3.g01195cf9f

Paolo Abeni

2023-Mar-30 10:18 UTC

head link

[PATCH net-next 7/8] virtio_net: introduce receive_mergeable_xdp()

Hi,

On Tue, 2023-03-28 at 20:04 +0800, Xuan Zhuo wrote:> The purpose of this patch is to simplify the receive_mergeable().
> Separate all the logic of XDP into a function.
> 
> Signed-off-by: Xuan Zhuo <xuanzhuo at linux.alibaba.com>
> ---
>  drivers/net/virtio_net.c | 128 +++++++++++++++++++++++----------------
>  1 file changed, 76 insertions(+), 52 deletions(-)
> 
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index 136131a7868a..c8978d8d8adb 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -1316,6 +1316,63 @@ static void *mergeable_xdp_prepare(struct
virtnet_info *vi,
>  	return page_address(xdp_page) + VIRTIO_XDP_HEADROOM;
>  }
>  
> +static struct sk_buff *receive_mergeable_xdp(struct net_device *dev,
> +					     struct virtnet_info *vi,
> +					     struct receive_queue *rq,
> +					     struct bpf_prog *xdp_prog,
> +					     void *buf,
> +					     void *ctx,
> +					     unsigned int len,
> +					     unsigned int *xdp_xmit,
> +					     struct virtnet_rq_stats *stats)
> +{
> +	struct virtio_net_hdr_mrg_rxbuf *hdr = buf;
> +	int 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 xdp_frags_truesz = 0;
> +	struct sk_buff *head_skb;
> +	unsigned int frame_sz;
> +	struct xdp_buff xdp;
> +	void *data;
> +	u32 act;
> +	int err;
> +
> +	data = mergeable_xdp_prepare(vi, rq, xdp_prog, ctx, &frame_sz,
&num_buf, &page,
> +				     offset, &len, hdr);
> +	if (!data)
> +		goto err_xdp;
> +
> +	err = virtnet_build_xdp_buff_mrg(dev, vi, rq, &xdp, data, len,
frame_sz,
> +					 &num_buf, &xdp_frags_truesz, stats);
> +	if (unlikely(err))
> +		goto err_xdp;
> +
> +	act = virtnet_xdp_handler(xdp_prog, &xdp, dev, xdp_xmit, stats);
> +
> +	switch (act) {
> +	case VIRTNET_XDP_RES_PASS:
> +		head_skb = build_skb_from_xdp_buff(dev, vi, &xdp, xdp_frags_truesz);
> +		if (unlikely(!head_skb))
> +			goto err_xdp;
> +		return head_skb;
> +
> +	case VIRTNET_XDP_RES_CONSUMED:
> +		return NULL;
> +
> +	case VIRTNET_XDP_RES_DROP:
> +		break;
> +	}
> +
> +err_xdp:
> +	put_page(page);
> +	mergeable_buf_free(rq, num_buf, dev, stats);
> +
> +	stats->xdp_drops++;
> +	stats->drops++;
> +	return NULL;
> +}
> +
>  static struct sk_buff *receive_mergeable(struct net_device *dev,
>  					 struct virtnet_info *vi,
>  					 struct receive_queue *rq,
> @@ -1325,21 +1382,22 @@ static struct sk_buff *receive_mergeable(struct
net_device *dev,
>  					 unsigned int *xdp_xmit,
>  					 struct virtnet_rq_stats *stats)
>  {
> -	struct virtio_net_hdr_mrg_rxbuf *hdr = buf;
> -	int num_buf = virtio16_to_cpu(vi->vdev, hdr->num_buffers);
> -	struct page *page = virt_to_head_page(buf);
> -	int offset = buf - page_address(page);
> -	struct sk_buff *head_skb, *curr_skb;
> -	struct bpf_prog *xdp_prog;
>  	unsigned int truesize = mergeable_ctx_to_truesize(ctx);
>  	unsigned int headroom = mergeable_ctx_to_headroom(ctx);
>  	unsigned int tailroom = headroom ? sizeof(struct skb_shared_info) : 0;
>  	unsigned int room = SKB_DATA_ALIGN(headroom + tailroom);
> -	unsigned int frame_sz;
> -	int err;
> +	struct virtio_net_hdr_mrg_rxbuf *hdr;
> +	struct sk_buff *head_skb, *curr_skb;
> +	struct bpf_prog *xdp_prog;
> +	struct page *page;
> +	int num_buf;
> +	int offset;
>  
>  	head_skb = NULL;
>  	stats->bytes += len - vi->hdr_len;
> +	hdr = buf;
> +	num_buf = virtio16_to_cpu(vi->vdev, hdr->num_buffers);
> +	page = virt_to_head_page(buf);
>  
>  	if (unlikely(len > truesize - room)) {
>  		pr_debug("%s: rx error: len %u exceeds truesize %lu\n",
> @@ -1348,51 +1406,21 @@ static struct sk_buff *receive_mergeable(struct
net_device *dev,
>  		goto err_skb;
>  	}
>  
> -	if (likely(!vi->xdp_enabled)) {
> -		xdp_prog = NULL;
> -		goto skip_xdp;
> -	}
> -
> -	rcu_read_lock();
> -	xdp_prog = rcu_dereference(rq->xdp_prog);
> -	if (xdp_prog) {
> -		unsigned int xdp_frags_truesz = 0;
> -		struct xdp_buff xdp;
> -		void *data;
> -		u32 act;
> -
> -		data = mergeable_xdp_prepare(vi, rq, xdp_prog, ctx, &frame_sz,
&num_buf, &page,
> -					     offset, &len, hdr);
> -		if (!data)
> -			goto err_xdp;
> -
> -		err = virtnet_build_xdp_buff_mrg(dev, vi, rq, &xdp, data, len,
frame_sz,
> -						 &num_buf, &xdp_frags_truesz, stats);
> -		if (unlikely(err))
> -			goto err_xdp;
> -
> -		act = virtnet_xdp_handler(xdp_prog, &xdp, dev, xdp_xmit, stats);
> -
> -		switch (act) {
> -		case VIRTNET_XDP_RES_PASS:
> -			head_skb = build_skb_from_xdp_buff(dev, vi, &xdp,
xdp_frags_truesz);
> -			if (unlikely(!head_skb))
> -				goto err_xdp;
> -
> +	if (likely(vi->xdp_enabled)) {
This changes the branch prediction hint compared to the existing code;
as we currently have:
	if (likely(!vi->xdp_enabled)) {


and I think it would be better avoid such change.

Thanks,

Paolo

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