[PATCH net-next v2 6/7] virtio-net, xsk: implement xsk wakeup callback

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

Since I did not find an interface to directly notify virtio to generate
a tx interrupt, I sent some data to trigger a new tx interrupt.

Another advantage of this is that the transmission delay will be
relatively small, and there is no need to wait for the tx interrupt to
start softirq.

Signed-off-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
---
 drivers/net/virtio_net.c | 51 ++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 51 insertions(+)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 42aa9ad..e552c2d 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -2841,6 +2841,56 @@ static int virtnet_xsk_run(struct send_queue *sq,
 	return ret;
 }
 
+static int virtnet_xsk_wakeup(struct net_device *dev, u32 qid, u32 flag)
+{
+	struct virtnet_info *vi = netdev_priv(dev);
+	struct send_queue *sq;
+	struct xsk_buff_pool *pool;
+	struct netdev_queue *txq;
+
+	if (!netif_running(dev))
+		return -ENETDOWN;
+
+	if (qid >= vi->curr_queue_pairs)
+		return -EINVAL;
+
+	sq = &vi->sq[qid];
+
+	rcu_read_lock();
+
+	pool = rcu_dereference(sq->xsk.pool);
+	if (!pool)
+		goto end;
+
+	if (test_and_set_bit(VIRTNET_STATE_XSK_WAKEUP, &sq->xsk.state))
+		goto end;
+
+	txq = netdev_get_tx_queue(dev, qid);
+
+	local_bh_disable();
+	__netif_tx_lock(txq, raw_smp_processor_id());
+
+	/* Send part of the package directly to reduce the delay in sending the
+	 * package, and this can actively trigger the tx interrupts.
+	 *
+	 * If the package is not processed, then continue processing in the
+	 * subsequent tx interrupt(virtnet_poll_tx).
+	 *
+	 * If no packet is sent out, the ring of the device is full. In this
+	 * case, we will still get a tx interrupt response. Then we will deal
+	 * with the subsequent packet sending work.
+	 */
+
+	virtnet_xsk_run(sq, pool, xsk_budget);
+
+	__netif_tx_unlock(txq);
+	local_bh_enable();
+
+end:
+	rcu_read_unlock();
+	return 0;
+}
+
 static int virtnet_get_phys_port_name(struct net_device *dev, char *buf,
 				      size_t len)
 {
@@ -2895,6 +2945,7 @@ static int virtnet_set_features(struct net_device *dev,
 	.ndo_vlan_rx_kill_vid = virtnet_vlan_rx_kill_vid,
 	.ndo_bpf		= virtnet_xdp,
 	.ndo_xdp_xmit		= virtnet_xdp_xmit,
+	.ndo_xsk_wakeup		= virtnet_xsk_wakeup,
 	.ndo_features_check	= passthru_features_check,
 	.ndo_get_phys_port_name	= virtnet_get_phys_port_name,
 	.ndo_set_features	= virtnet_set_features,
-- 
1.8.3.1