netdev - [PATCH 3/3] virtio_net: split XDP_TX kick and XDP

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Message-ID: <153002759867.15389.3727307011205722452.stgit@firesoul>
Date:   Tue, 26 Jun 2018 17:39:58 +0200
From:   Jesper Dangaard Brouer <brouer@...hat.com>
To:     netdev@...r.kernel.org, Jesper Dangaard Brouer <brouer@...hat.com>
Cc:     John Fastabend <john.fastabend@...il.com>,
        Jason Wang <jasowang@...hat.com>,
        Daniel Borkmann <borkmann@...earbox.net>,
        BjörnTöpel <bjorn.topel@...el.com>,
        Alexei Starovoitov <alexei.starovoitov@...il.com>
Subject: [PATCH 3/3] virtio_net: split XDP_TX kick and XDP_REDIRECT map
 flushing

The driver was combining XDP_TX virtqueue_kick and XDP_REDIRECT
map flushing (xdp_do_flush_map).  This is suboptimal, these two
flush operations should be kept separate.

The suboptimal behavior was introduced in commit 9267c430c6b6
("virtio-net: add missing virtqueue kick when flushing packets").

Fixes: 9267c430c6b6 ("virtio-net: add missing virtqueue kick when flushing packets")
Signed-off-by: Jesper Dangaard Brouer <brouer@...hat.com>
---
 drivers/net/virtio_net.c |   30 +++++++++++++++++++-----------
 1 file changed, 19 insertions(+), 11 deletions(-)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 1619ee3070b6..ae47ecf80c2d 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -53,6 +53,10 @@ module_param(napi_tx, bool, 0644);
 /* Amount of XDP headroom to prepend to packets for use by xdp_adjust_head */
 #define VIRTIO_XDP_HEADROOM 256
 
+/* Separating two types of XDP xmit */
+#define VIRTIO_XDP_TX		BIT(0)
+#define VIRTIO_XDP_REDIR	BIT(1)
+
 /* RX packet size EWMA. The average packet size is used to determine the packet
  * buffer size when refilling RX rings. As the entire RX ring may be refilled
  * at once, the weight is chosen so that the EWMA will be insensitive to short-
@@ -582,7 +586,7 @@ static struct sk_buff *receive_small(struct net_device *dev,
 				     struct receive_queue *rq,
 				     void *buf, void *ctx,
 				     unsigned int len,
-				     bool *xdp_xmit)
+				     unsigned int *xdp_xmit)
 {
 	struct sk_buff *skb;
 	struct bpf_prog *xdp_prog;
@@ -654,14 +658,14 @@ static struct sk_buff *receive_small(struct net_device *dev,
 				trace_xdp_exception(vi->dev, xdp_prog, act);
 				goto err_xdp;
 			}
-			*xdp_xmit = true;
+			*xdp_xmit |= VIRTIO_XDP_TX;
 			rcu_read_unlock();
 			goto xdp_xmit;
 		case XDP_REDIRECT:
 			err = xdp_do_redirect(dev, &xdp, xdp_prog);
 			if (err)
 				goto err_xdp;
-			*xdp_xmit = true;
+			*xdp_xmit |= VIRTIO_XDP_REDIR;
 			rcu_read_unlock();
 			goto xdp_xmit;
 		default:
@@ -723,7 +727,7 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
 					 void *buf,
 					 void *ctx,
 					 unsigned int len,
-					 bool *xdp_xmit)
+					 unsigned int *xdp_xmit)
 {
 	struct virtio_net_hdr_mrg_rxbuf *hdr = buf;
 	u16 num_buf = virtio16_to_cpu(vi->vdev, hdr->num_buffers);
@@ -818,7 +822,7 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
 					put_page(xdp_page);
 				goto err_xdp;
 			}
-			*xdp_xmit = true;
+			*xdp_xmit |= VIRTIO_XDP_TX;
 			if (unlikely(xdp_page != page))
 				put_page(page);
 			rcu_read_unlock();
@@ -830,7 +834,7 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
 					put_page(xdp_page);
 				goto err_xdp;
 			}
-			*xdp_xmit = true;
+			*xdp_xmit |= VIRTIO_XDP_REDIR;
 			if (unlikely(xdp_page != page))
 				put_page(page);
 			rcu_read_unlock();
@@ -939,7 +943,8 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
 }
 
 static int receive_buf(struct virtnet_info *vi, struct receive_queue *rq,
-		       void *buf, unsigned int len, void **ctx, bool *xdp_xmit)
+		       void *buf, unsigned int len, void **ctx,
+		       unsigned int *xdp_xmit)
 {
 	struct net_device *dev = vi->dev;
 	struct sk_buff *skb;
@@ -1232,7 +1237,8 @@ static void refill_work(struct work_struct *work)
 	}
 }
 
-static int virtnet_receive(struct receive_queue *rq, int budget, bool *xdp_xmit)
+static int virtnet_receive(struct receive_queue *rq, int budget,
+			   unsigned int *xdp_xmit)
 {
 	struct virtnet_info *vi = rq->vq->vdev->priv;
 	unsigned int len, received = 0, bytes = 0;
@@ -1321,7 +1327,7 @@ static int virtnet_poll(struct napi_struct *napi, int budget)
 	struct virtnet_info *vi = rq->vq->vdev->priv;
 	struct send_queue *sq;
 	unsigned int received, qp;
-	bool xdp_xmit = false;
+	unsigned int xdp_xmit = 0;
 
 	virtnet_poll_cleantx(rq);
 
@@ -1331,12 +1337,14 @@ static int virtnet_poll(struct napi_struct *napi, int budget)
 	if (received < budget)
 		virtqueue_napi_complete(napi, rq->vq, received);
 
-	if (xdp_xmit) {
+	if (xdp_xmit & VIRTIO_XDP_REDIR)
+		xdp_do_flush_map();
+
+	if (xdp_xmit & VIRTIO_XDP_TX) {
 		qp = vi->curr_queue_pairs - vi->xdp_queue_pairs +
 		     smp_processor_id();
 		sq = &vi->sq[qp];
 		virtqueue_kick(sq->vq);
-		xdp_do_flush_map();
 	}
 
 	return received;