Date:   Wed, 26 Dec 2018 12:27:49 -0800
From:   William Tu <u9012063@...il.com>
To:     bjorn.topel@...il.com, magnus.karlsson@...il.com, ast@...nel.org,
        daniel@...earbox.net, netdev@...r.kernel.org,
        makita.toshiaki@....ntt.co.jp, yihung.wei@...il.com,
        magnus.karlsson@...el.com
Subject: [PATCH bpf-next RFCv3 2/6] veth: support AF_XDP TX copy-mode.

The patch adds support for AF_XDP async xmit.  Users can use
AF_XDP on both sides of the veth and get better performance, with
the cost of ksoftirqd doing the xmit.  The veth_xsk_async_xmit
simply kicks the napi function, veth_poll, to receive the packets
that are on the umem transmit ring at the _peer_ side.

Tested using two namespaces, one runs xdpsock and the other runs
xdp_rxq_info.  A simple script comparing the performance with/without
AF_XDP shows improvement from 724Kpps to 1.1Mpps.

  ip netns add at_ns0
  ip link add p0 type veth peer name p1
  ip link set p0 netns at_ns0
  ip link set dev p1 up
  ip netns exec at_ns0 ip link set dev p0 up

  # receiver
  ip netns exec at_ns0 xdp_rxq_info --dev p0 --action XDP_DROP

  # sender
  xdpsock -i p1 -t -N -z
  or
  xdpsock -i p1 -t -S

Signed-off-by: William Tu <u9012063@...il.com>
---
 drivers/net/veth.c | 200 ++++++++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 199 insertions(+), 1 deletion(-)

diff --git a/drivers/net/veth.c b/drivers/net/veth.c
index f412ea1cef18..10cf9ded59f1 100644
--- a/drivers/net/veth.c
+++ b/drivers/net/veth.c
@@ -25,6 +25,10 @@
 #include <linux/ptr_ring.h>
 #include <linux/bpf_trace.h>
 #include <linux/net_tstamp.h>
+#include <net/xdp_sock.h>
+#include <linux/mm.h>
+#include <linux/slab.h>
+#include <net/page_pool.h>
 
 #define DRV_NAME	"veth"
 #define DRV_VERSION	"1.0"
@@ -53,6 +57,8 @@ struct veth_rq {
 	bool			rx_notify_masked;
 	struct ptr_ring		xdp_ring;
 	struct xdp_rxq_info	xdp_rxq;
+	struct xdp_umem *xsk_umem;
+	u16 qid;
 };
 
 struct veth_priv {
@@ -737,11 +743,95 @@ static int veth_xdp_rcv(struct veth_rq *rq, int budget, unsigned int *xdp_xmit)
 	return done;
 }
 
+static int veth_xsk_poll(struct napi_struct *napi, int budget)
+{
+	struct veth_priv *priv, *peer_priv;
+	struct net_device *dev, *peer_dev;
+	struct veth_rq *peer_rq;
+	struct veth_rq *rq =
+		container_of(napi, struct veth_rq, xdp_napi);
+	int done = 0;
+
+	dev = rq->dev;
+	priv = netdev_priv(dev);
+	peer_dev = priv->peer;
+	peer_priv = netdev_priv(peer_dev);
+	peer_rq = &peer_priv->rq[rq->qid];
+
+	while (peer_rq->xsk_umem && budget--) {
+		unsigned int inner_xdp_xmit = 0;
+		unsigned int metasize = 0;
+		struct xdp_frame *xdpf;
+		bool dropped = false;
+		struct sk_buff *skb;
+		struct page *page;
+		void *vaddr;
+		void *addr;
+		u32 len;
+
+		if (!xsk_umem_consume_tx_virtual(peer_rq->xsk_umem, &vaddr, &len))
+			break;
+
+		page = dev_alloc_page();
+		if (!page) {
+			xsk_umem_complete_tx(peer_rq->xsk_umem, 1);
+			xsk_umem_consume_tx_done(peer_rq->xsk_umem);
+			return -ENOMEM;
+		}
+
+		addr = page_to_virt(page);
+		xdpf = addr;
+		memset(xdpf, 0, sizeof(*xdpf));
+
+		addr += sizeof(*xdpf);
+		memcpy(addr, vaddr, len);
+
+		xdpf->data = addr + metasize;
+		xdpf->len = len;
+		xdpf->headroom = 0;
+		xdpf->metasize = metasize;
+		xdpf->mem.type = MEM_TYPE_PAGE_SHARED;
+
+		/* put into rq */
+		skb = veth_xdp_rcv_one(rq, xdpf, &inner_xdp_xmit);
+		if (!skb) {
+			/* Peer side has XDP program attached */
+			if (inner_xdp_xmit & VETH_XDP_TX) {
+				/* Not supported */
+				pr_warn("veth: peer XDP_TX not supported\n");
+				xdp_return_frame(xdpf);
+				dropped = true;
+				goto skip_tx;
+			} else if (inner_xdp_xmit & VETH_XDP_REDIR) {
+				xdp_do_flush_map();
+			} else {
+				dropped = true;
+			}
+		} else {
+			napi_gro_receive(&rq->xdp_napi, skb);
+		}
+skip_tx:
+		xsk_umem_complete_tx(peer_rq->xsk_umem, 1);
+		xsk_umem_consume_tx_done(peer_rq->xsk_umem);
+
+		/* update rq stats */
+		u64_stats_update_begin(&rq->stats.syncp);
+		rq->stats.xdp_packets++;
+		rq->stats.xdp_bytes += len;
+		if (dropped)
+			rq->stats.xdp_drops++;
+		u64_stats_update_end(&rq->stats.syncp);
+		done++;
+	}
+	return done;
+}
+
 static int veth_poll(struct napi_struct *napi, int budget)
 {
 	struct veth_rq *rq =
 		container_of(napi, struct veth_rq, xdp_napi);
 	unsigned int xdp_xmit = 0;
+	int tx_done;
 	int done;
 
 	xdp_set_return_frame_no_direct();
@@ -756,13 +846,17 @@ static int veth_poll(struct napi_struct *napi, int budget)
 		}
 	}
 
+	tx_done = veth_xsk_poll(napi, budget);
+	if (tx_done > 0)
+		done += tx_done;
+
 	if (xdp_xmit & VETH_XDP_TX)
 		veth_xdp_flush(rq->dev);
 	if (xdp_xmit & VETH_XDP_REDIR)
 		xdp_do_flush_map();
 	xdp_clear_return_frame_no_direct();
 
-	return done;
+	return done > budget ? budget : done;
 }
 
 static int veth_napi_add(struct net_device *dev)
@@ -776,6 +870,7 @@ static int veth_napi_add(struct net_device *dev)
 		err = ptr_ring_init(&rq->xdp_ring, VETH_RING_SIZE, GFP_KERNEL);
 		if (err)
 			goto err_xdp_ring;
+		rq->qid = i;
 	}
 
 	for (i = 0; i < dev->real_num_rx_queues; i++) {
@@ -812,6 +907,7 @@ static void veth_napi_del(struct net_device *dev)
 		netif_napi_del(&rq->xdp_napi);
 		rq->rx_notify_masked = false;
 		ptr_ring_cleanup(&rq->xdp_ring, veth_ptr_free);
+		rq->qid = -1;
 	}
 }
 
@@ -836,6 +932,7 @@ static int veth_enable_xdp(struct net_device *dev)
 
 			/* Save original mem info as it can be overwritten */
 			rq->xdp_mem = rq->xdp_rxq.mem;
+			rq->qid = i;
 		}
 
 		err = veth_napi_add(dev);
@@ -1115,6 +1212,84 @@ static u32 veth_xdp_query(struct net_device *dev)
 	return 0;
 }
 
+int veth_xsk_umem_query(struct net_device *dev, struct xdp_umem **umem,
+			u16 qid)
+{
+	struct xdp_umem *queried_umem;
+
+	queried_umem = xdp_get_umem_from_qid(dev, qid);
+
+	if (!queried_umem)
+		return -EINVAL;
+
+	*umem = queried_umem;
+	return 0;
+}
+
+static int veth_xsk_umem_enable(struct net_device *dev,
+				struct xdp_umem *umem,
+				u16 qid)
+{
+	struct veth_priv *priv = netdev_priv(dev);
+	struct xdp_umem_fq_reuse *reuseq;
+	int err = 0;
+
+	if (qid >= dev->real_num_rx_queues)
+		return -EINVAL;
+
+	reuseq = xsk_reuseq_prepare(priv->rq[0].xdp_ring.size);
+	if (!reuseq)
+		return -ENOMEM;
+
+	xsk_reuseq_free(xsk_reuseq_swap(umem, reuseq));
+
+	priv->rq[qid].xsk_umem = umem;
+
+	return err;
+}
+
+static int veth_xsk_umem_disable(struct net_device *dev,
+				 u16 qid)
+{
+	struct veth_priv *priv = netdev_priv(dev);
+	struct xdp_umem *umem;
+
+	umem = xdp_get_umem_from_qid(dev, qid);
+	if (!umem)
+		return -EINVAL;
+
+	priv->rq[qid].xsk_umem = NULL;
+	return 0;
+}
+
+int veth_xsk_umem_setup(struct net_device *dev, struct xdp_umem *umem,
+			u16 qid)
+{
+	return umem ? veth_xsk_umem_enable(dev, umem, qid) :
+		      veth_xsk_umem_disable(dev, qid);
+}
+
+int veth_xsk_async_xmit(struct net_device *dev, u32 qid)
+{
+	struct veth_priv *priv, *peer_priv;
+	struct net_device *peer_dev;
+	struct veth_rq *peer_rq;
+
+	priv = netdev_priv(dev);
+	peer_dev = priv->peer;
+	peer_priv = netdev_priv(peer_dev);
+	peer_rq = &peer_priv->rq[qid];
+
+	if (qid >= dev->real_num_rx_queues)
+		return -ENXIO;
+
+	/* Schedule the peer side NAPI to receive */
+	if (!napi_if_scheduled_mark_missed(&peer_rq->xdp_napi))
+		napi_schedule(&peer_rq->xdp_napi);
+
+	return 0;
+}
+
 static int veth_xdp(struct net_device *dev, struct netdev_bpf *xdp)
 {
 	switch (xdp->command) {
@@ -1123,6 +1298,28 @@ static int veth_xdp(struct net_device *dev, struct netdev_bpf *xdp)
 	case XDP_QUERY_PROG:
 		xdp->prog_id = veth_xdp_query(dev);
 		return 0;
+	case XDP_QUERY_XSK_UMEM:
+		return veth_xsk_umem_query(dev, &xdp->xsk.umem,
+					   xdp->xsk.queue_id);
+	case XDP_SETUP_XSK_UMEM: {
+		struct veth_priv *priv;
+		int err;
+
+		/* Enable NAPI on both sides, by enabling
+		 * their XDP.
+		 */
+		err = veth_enable_xdp(dev);
+		if (err)
+			return err;
+
+		priv = netdev_priv(dev);
+		err = veth_enable_xdp(priv->peer);
+		if (err)
+			return err;
+
+		return veth_xsk_umem_setup(dev, xdp->xsk.umem,
+					   xdp->xsk.queue_id);
+	}
 	default:
 		return -EINVAL;
 	}
@@ -1145,6 +1342,7 @@ static const struct net_device_ops veth_netdev_ops = {
 	.ndo_set_rx_headroom	= veth_set_rx_headroom,
 	.ndo_bpf		= veth_xdp,
 	.ndo_xdp_xmit		= veth_xdp_xmit,
+	.ndo_xsk_async_xmit	= veth_xsk_async_xmit,
 };
 
 #define VETH_FEATURES (NETIF_F_SG | NETIF_F_FRAGLIST | NETIF_F_HW_CSUM | \
-- 
2.7.4

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