netdev - [PATCH net-next v4 07/10] virtio-net: virtnet_poll

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Date:   Tue, 13 Apr 2021 11:15:20 +0800
From:   Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
To:     netdev@...r.kernel.org
Cc:     "Michael S. Tsirkin" <mst@...hat.com>,
        Jason Wang <jasowang@...hat.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Björn Töpel <bjorn@...nel.org>,
        Magnus Karlsson <magnus.karlsson@...el.com>,
        Jonathan Lemon <jonathan.lemon@...il.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Jesper Dangaard Brouer <hawk@...nel.org>,
        John Fastabend <john.fastabend@...il.com>,
        virtualization@...ts.linux-foundation.org, bpf@...r.kernel.org,
        "dust . li" <dust.li@...ux.alibaba.com>
Subject: [PATCH net-next v4 07/10] virtio-net: virtnet_poll_tx support budget check

virtnet_poll_tx() check the work done like other network card drivers.

When work < budget, napi_poll() in dev.c will exit directly. And
virtqueue_napi_complete() will be called to close napi. If closing napi
fails or there is still data to be processed, virtqueue_napi_complete()
will make napi schedule again, and no conflicts with the logic of
napi_poll().

When work == budget, virtnet_poll_tx() will return the var 'work', and
the napi_poll() in dev.c will re-add napi to the queue.

The purpose of this patch is to support xsk xmit in virtio_poll_tx for
subsequent patch.

Signed-off-by: Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
---
 drivers/net/virtio_net.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index f3752b254965..f52a25091322 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -1529,6 +1529,7 @@ static int virtnet_poll_tx(struct napi_struct *napi, int budget)
 	struct virtnet_info *vi = sq->vq->vdev->priv;
 	unsigned int index = vq2txq(sq->vq);
 	struct netdev_queue *txq;
+	int work_done = 0;
 
 	if (unlikely(is_xdp_raw_buffer_queue(vi, index))) {
 		/* We don't need to enable cb for XDP */
@@ -1541,12 +1542,13 @@ static int virtnet_poll_tx(struct napi_struct *napi, int budget)
 	free_old_xmit(sq, true);
 	__netif_tx_unlock(txq);
 
-	virtqueue_napi_complete(napi, sq->vq, 0);
+	if (work_done < budget)
+		virtqueue_napi_complete(napi, sq->vq, 0);
 
 	if (sq->vq->num_free >= 2 + MAX_SKB_FRAGS)
 		netif_tx_wake_queue(txq);
 
-	return 0;
+	return work_done;
 }
 
 static int xmit_skb(struct send_queue *sq, struct sk_buff *skb)
-- 
2.31.0