Re: [PATCH net-next v2 3/4] virtio_net: Map NAPIs to queues

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

On Thu, 16 Jan 2025 05:52:58 +0000, Joe Damato <jdamato@fastly.com> 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@fastly.com>
> ---
>  v2:
>    - Eliminate RTNL code paths using the API Jakub introduced in patch 1
>      of this v2.
>    - Added virtnet_napi_disable to reduce code duplication as
>      suggested by Jason Wang.
>
>  drivers/net/virtio_net.c | 34 +++++++++++++++++++++++++++++-----
>  1 file changed, 29 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index cff18c66b54a..c6fda756dd07 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -2803,9 +2803,18 @@ static void virtnet_napi_do_enable(struct virtqueue *vq,
>  	local_bh_enable();
>  }
>
> -static void virtnet_napi_enable(struct virtqueue *vq, struct napi_struct *napi)
> +static void virtnet_napi_enable(struct virtqueue *vq,
> +				struct napi_struct *napi)
>  {
> +	struct virtnet_info *vi = vq->vdev->priv;
> +	int q = vq2rxq(vq);
> +	u16 curr_qs;
> +
>  	virtnet_napi_do_enable(vq, napi);
> +
> +	curr_qs = vi->curr_queue_pairs - vi->xdp_queue_pairs;
> +	if (!vi->xdp_enabled || q < curr_qs)
> +		netif_queue_set_napi(vi->dev, q, NETDEV_QUEUE_TYPE_RX, napi);

So what case the check of xdp_enabled is for?

And I think we should merge this to last commit.

Thanks.

>  }
>
>  static void virtnet_napi_tx_enable(struct virtnet_info *vi,
> @@ -2826,6 +2835,20 @@ static void virtnet_napi_tx_enable(struct virtnet_info *vi,
>  	virtnet_napi_do_enable(vq, napi);
>  }
>
> +static void virtnet_napi_disable(struct virtqueue *vq,
> +				 struct napi_struct *napi)
> +{
> +	struct virtnet_info *vi = vq->vdev->priv;
> +	int q = vq2rxq(vq);
> +	u16 curr_qs;
> +
> +	curr_qs = vi->curr_queue_pairs - vi->xdp_queue_pairs;
> +	if (!vi->xdp_enabled || q < curr_qs)
> +		netif_queue_set_napi(vi->dev, q, NETDEV_QUEUE_TYPE_RX, NULL);
> +
> +	napi_disable(napi);
> +}
> +
>  static void virtnet_napi_tx_disable(struct napi_struct *napi)
>  {
>  	if (napi->weight)
> @@ -2842,7 +2865,8 @@ static void refill_work(struct work_struct *work)
>  	for (i = 0; i < vi->curr_queue_pairs; i++) {
>  		struct receive_queue *rq = &vi->rq[i];
>
> -		napi_disable(&rq->napi);
> +		virtnet_napi_disable(rq->vq, &rq->napi);
> +
>  		still_empty = !try_fill_recv(vi, rq, GFP_KERNEL);
>  		virtnet_napi_enable(rq->vq, &rq->napi);
>
> @@ -3042,7 +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);
> -	napi_disable(&vi->rq[qp_index].napi);
> +	virtnet_napi_disable(vi->rq[qp_index].vq, &vi->rq[qp_index].napi);
>  	xdp_rxq_info_unreg(&vi->rq[qp_index].xdp_rxq);
>  }
>
> @@ -3313,7 +3337,7 @@ static void virtnet_rx_pause(struct virtnet_info *vi, struct receive_queue *rq)
>  	bool running = netif_running(vi->dev);
>
>  	if (running) {
> -		napi_disable(&rq->napi);
> +		virtnet_napi_disable(rq->vq, &rq->napi);
>  		virtnet_cancel_dim(vi, &rq->dim);
>  	}
>  }
> @@ -5932,7 +5956,7 @@ 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++) {
> -			napi_disable(&vi->rq[i].napi);
> +			virtnet_napi_disable(vi->rq[i].vq, &vi->rq[i].napi);
>  			virtnet_napi_tx_disable(&vi->sq[i].napi);
>  		}
>  	}
> --
> 2.25.1
>