[PATCH net-next v2 4/7] virtio-net, xsk: support xsk enable/disable

[Xuan Zhuo <xuanzhuo@linux.alibaba.com>]

When enable, a certain number of struct virtnet_xsk_hdr is allocated to
save the information of each packet and virtio hdr.This number is the
limit of the received module parameters.

When struct virtnet_xsk_hdr is used up, or the sq->vq->num_free of
virtio-net is too small, it will be considered that the device is busy.

* xsk_num_max: the xsk.hdr max num
* xsk_num_percent: the max hdr num be the percent of the virtio ring
  size. The real xsk hdr num will the min of xsk_num_max and the percent
  of the num of virtio ring
* xsk_budget: the budget for xsk run

Signed-off-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
---
 drivers/net/virtio_net.c | 97 ++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 97 insertions(+)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 9013328..a62d456 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -22,10 +22,19 @@
 #include <net/route.h>
 #include <net/xdp.h>
 #include <net/net_failover.h>
+#include <net/xdp_sock_drv.h>
 
 static int napi_weight = NAPI_POLL_WEIGHT;
 module_param(napi_weight, int, 0444);
 
+static int xsk_num_max     = 1024;
+static int xsk_num_percent = 80;
+static int xsk_budget      = 128;
+
+module_param(xsk_num_max,     int, 0644);
+module_param(xsk_num_percent, int, 0644);
+module_param(xsk_budget,      int, 0644);
+
 static bool csum = true, gso = true, napi_tx = true;
 module_param(csum, bool, 0444);
 module_param(gso, bool, 0444);
@@ -149,6 +158,15 @@ struct send_queue {
 	struct virtnet_sq_stats stats;
 
 	struct napi_struct napi;
+
+	struct {
+		struct xsk_buff_pool   __rcu *pool;
+		struct virtnet_xsk_hdr __rcu *hdr;
+
+		u64                    hdr_con;
+		u64                    hdr_pro;
+		u64                    hdr_n;
+	} xsk;
 };
 
 /* Internal representation of a receive virtqueue */
@@ -2540,11 +2558,90 @@ static int virtnet_xdp_set(struct net_device *dev, struct bpf_prog *prog,
 	return err;
 }
 
+static int virtnet_xsk_pool_enable(struct net_device *dev,
+				   struct xsk_buff_pool *pool,
+				   u16 qid)
+{
+	struct virtnet_info *vi = netdev_priv(dev);
+	struct send_queue *sq = &vi->sq[qid];
+	struct virtnet_xsk_hdr *hdr;
+	int n, ret = 0;
+
+	if (qid >= dev->real_num_rx_queues || qid >= dev->real_num_tx_queues)
+		return -EINVAL;
+
+	if (qid >= vi->curr_queue_pairs)
+		return -EINVAL;
+
+	rcu_read_lock();
+
+	ret = -EBUSY;
+	if (rcu_dereference(sq->xsk.pool))
+		goto end;
+
+	/* check last xsk wait for hdr been free */
+	if (rcu_dereference(sq->xsk.hdr))
+		goto end;
+
+	n = virtqueue_get_vring_size(sq->vq);
+	n = min(xsk_num_max, n * (xsk_num_percent % 100) / 100);
+
+	ret = -ENOMEM;
+	hdr = kcalloc(n, sizeof(struct virtnet_xsk_hdr), GFP_ATOMIC);
+	if (!hdr)
+		goto end;
+
+	memset(&sq->xsk, 0, sizeof(sq->xsk));
+
+	sq->xsk.hdr_pro = n;
+	sq->xsk.hdr_n   = n;
+
+	rcu_assign_pointer(sq->xsk.pool, pool);
+	rcu_assign_pointer(sq->xsk.hdr, hdr);
+
+	ret = 0;
+end:
+	rcu_read_unlock();
+
+	return ret;
+}
+
+static int virtnet_xsk_pool_disable(struct net_device *dev, u16 qid)
+{
+	struct virtnet_info *vi = netdev_priv(dev);
+	struct send_queue *sq = &vi->sq[qid];
+	struct virtnet_xsk_hdr *hdr = NULL;
+
+	if (qid >= dev->real_num_rx_queues || qid >= dev->real_num_tx_queues)
+		return -EINVAL;
+
+	if (qid >= vi->curr_queue_pairs)
+		return -EINVAL;
+
+	rcu_assign_pointer(sq->xsk.pool, NULL);
+
+	if (sq->xsk.hdr_pro - sq->xsk.hdr_con == sq->xsk.hdr_n)
+		hdr = rcu_replace_pointer(sq->xsk.hdr, hdr, true);
+
+	synchronize_rcu(); /* Sync with the XSK wakeup and with NAPI. */
+
+	kfree(hdr);
+
+	return 0;
+}
+
 static int virtnet_xdp(struct net_device *dev, struct netdev_bpf *xdp)
 {
 	switch (xdp->command) {
 	case XDP_SETUP_PROG:
 		return virtnet_xdp_set(dev, xdp->prog, xdp->extack);
+	case XDP_SETUP_XSK_POOL:
+		xdp->xsk.need_dma = false;
+		if (xdp->xsk.pool)
+			return virtnet_xsk_pool_enable(dev, xdp->xsk.pool,
+						       xdp->xsk.queue_id);
+		else
+			return virtnet_xsk_pool_disable(dev, xdp->xsk.queue_id);
 	default:
 		return -EINVAL;
 	}
-- 
1.8.3.1