netdev - Re: [PATCH net-next 3/3] virtio

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Message-ID: <60af36b0-a835-4ba1-994d-2aad527ed4e5@engleder-embedded.com>
Date: Fri, 10 Jan 2025 23:25:39 +0100
From: Gerhard Engleder <gerhard@...leder-embedded.com>
To: Joe Damato <jdamato@...tly.com>, netdev@...r.kernel.org
Cc: mkarsten@...terloo.ca, "Michael S. Tsirkin" <mst@...hat.com>,
 Jason Wang <jasowang@...hat.com>, Xuan Zhuo <xuanzhuo@...ux.alibaba.com>,
 Eugenio Pérez <eperezma@...hat.com>,
 Andrew Lunn <andrew+netdev@...n.ch>, "David S. Miller"
 <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>,
 Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
 "open list:VIRTIO CORE AND NET DRIVERS" <virtualization@...ts.linux.dev>,
 open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH net-next 3/3] virtio_net: Map NAPIs to queues

On 10.01.25 21:26, Joe Damato wrote:
> Use netif_queue_set_napi to map NAPIs to queue IDs so that the mapping
> can be accessed by user apps.
> 
> $ ethtool -i ens4 | grep driver
> driver: virtio_net
> 
> $ sudo ethtool -L ens4 combined 4
> 
> $ ./tools/net/ynl/pyynl/cli.py \
>         --spec Documentation/netlink/specs/netdev.yaml \
>         --dump queue-get --json='{"ifindex": 2}'
> [{'id': 0, 'ifindex': 2, 'napi-id': 8289, 'type': 'rx'},
>   {'id': 1, 'ifindex': 2, 'napi-id': 8290, 'type': 'rx'},
>   {'id': 2, 'ifindex': 2, 'napi-id': 8291, 'type': 'rx'},
>   {'id': 3, 'ifindex': 2, 'napi-id': 8292, 'type': 'rx'},
>   {'id': 0, 'ifindex': 2, 'type': 'tx'},
>   {'id': 1, 'ifindex': 2, 'type': 'tx'},
>   {'id': 2, 'ifindex': 2, 'type': 'tx'},
>   {'id': 3, 'ifindex': 2, 'type': 'tx'}]
> 
> Note that virtio_net has TX-only NAPIs which do not have NAPI IDs, so
> the lack of 'napi-id' in the above output is expected.
> 
> Signed-off-by: Joe Damato <jdamato@...tly.com>
> ---
>   drivers/net/virtio_net.c | 29 ++++++++++++++++++++++++++---
>   1 file changed, 26 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index 4e88d352d3eb..8f0f26cc5a94 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -2804,14 +2804,28 @@ static void virtnet_napi_do_enable(struct virtqueue *vq,
>   }
>   
>   static void virtnet_napi_enable_lock(struct virtqueue *vq,
> -				     struct napi_struct *napi)
> +				     struct napi_struct *napi,
> +				     bool need_rtnl)
>   {
> +	struct virtnet_info *vi = vq->vdev->priv;
> +	int q = vq2rxq(vq);
> +
>   	virtnet_napi_do_enable(vq, napi);
> +
> +	if (q < vi->curr_queue_pairs) {
> +		if (need_rtnl)
> +			rtnl_lock();
> +
> +		netif_queue_set_napi(vi->dev, q, NETDEV_QUEUE_TYPE_RX, napi);
> +
> +		if (need_rtnl)
> +			rtnl_unlock();
> +	}
>   }
>   
>   static void virtnet_napi_enable(struct virtqueue *vq, struct napi_struct *napi)
>   {
> -	virtnet_napi_enable_lock(vq, napi);
> +	virtnet_napi_enable_lock(vq, napi, false);
>   }
>   
>   static void virtnet_napi_tx_enable(struct virtnet_info *vi,
> @@ -2848,9 +2862,13 @@ static void refill_work(struct work_struct *work)
>   	for (i = 0; i < vi->curr_queue_pairs; i++) {
>   		struct receive_queue *rq = &vi->rq[i];
>   
> +		rtnl_lock();
> +		netif_queue_set_napi(vi->dev, i, NETDEV_QUEUE_TYPE_RX, NULL);
> +		rtnl_unlock();
>   		napi_disable(&rq->napi);
> +
>   		still_empty = !try_fill_recv(vi, rq, GFP_KERNEL);
> -		virtnet_napi_enable_lock(rq->vq, &rq->napi);
> +		virtnet_napi_enable_lock(rq->vq, &rq->napi, true);
>   
>   		/* In theory, this can happen: if we don't get any buffers in
>   		 * we will *never* try to fill again.
> @@ -3048,6 +3066,7 @@ static int virtnet_poll(struct napi_struct *napi, int budget)
>   static void virtnet_disable_queue_pair(struct virtnet_info *vi, int qp_index)
>   {
>   	virtnet_napi_tx_disable(&vi->sq[qp_index].napi);
> +	netif_queue_set_napi(vi->dev, qp_index, NETDEV_QUEUE_TYPE_RX, NULL);
>   	napi_disable(&vi->rq[qp_index].napi);
>   	xdp_rxq_info_unreg(&vi->rq[qp_index].xdp_rxq);
>   }
> @@ -3317,8 +3336,10 @@ static netdev_tx_t start_xmit(struct sk_buff *skb, struct net_device *dev)
>   static void virtnet_rx_pause(struct virtnet_info *vi, struct receive_queue *rq)
>   {
>   	bool running = netif_running(vi->dev);
> +	int q = vq2rxq(rq->vq);
>   
>   	if (running) {
> +		netif_queue_set_napi(vi->dev, q, NETDEV_QUEUE_TYPE_RX, NULL);
>   		napi_disable(&rq->napi);
>   		virtnet_cancel_dim(vi, &rq->dim);
>   	}
> @@ -5943,6 +5964,8 @@ static int virtnet_xdp_set(struct net_device *dev, struct bpf_prog *prog,
>   	/* Make sure NAPI is not using any XDP TX queues for RX. */
>   	if (netif_running(dev)) {
>   		for (i = 0; i < vi->max_queue_pairs; i++) {
> +			netif_queue_set_napi(vi->dev, i, NETDEV_QUEUE_TYPE_RX,
> +					     NULL);
>   			napi_disable(&vi->rq[i].napi);
>   			virtnet_napi_tx_disable(&vi->sq[i].napi);
>   		}

Reviewed-by: Gerhard Engleder <gerhard@...leder-embedded.com>