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Message-ID: <CACGkMEv6y+TkZnWWLPG4UE59iyREhkiaby8kj==cnp=6chmu+w@mail.gmail.com>
Date: Wed, 26 Feb 2025 13:48:50 +0800
From: Jason Wang <jasowang@...hat.com>
To: Joe Damato <jdamato@...tly.com>
Cc: netdev@...r.kernel.org, mkarsten@...terloo.ca,
gerhard@...leder-embedded.com, xuanzhuo@...ux.alibaba.com, kuba@...nel.org,
"Michael S. Tsirkin" <mst@...hat.com>, Eugenio Pérez <eperezma@...hat.com>,
Andrew Lunn <andrew+netdev@...n.ch>, "David S. Miller" <davem@...emloft.net>,
Eric Dumazet <edumazet@...gle.com>, 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 v4 3/4] virtio-net: Map NAPIs to queues
On Tue, Feb 25, 2025 at 10:05 AM Joe Damato <jdamato@...tly.com> wrote:
>
> Use netif_queue_set_napi to map NAPIs to queue IDs so that the mapping
> can be accessed by user apps, taking care to hold RTNL as needed.
I may miss something but I wonder whether letting the caller hold the
lock is better.
More below.
>
> $ 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 | 73 ++++++++++++++++++++++++++++------------
> 1 file changed, 52 insertions(+), 21 deletions(-)
>
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index e578885c1093..13bb4a563073 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -2807,6 +2807,20 @@ static void skb_recv_done(struct virtqueue *rvq)
> virtqueue_napi_schedule(&rq->napi, rvq);
> }
>
> +static void virtnet_queue_set_napi(struct net_device *dev,
> + struct napi_struct *napi,
> + enum netdev_queue_type q_type, int qidx,
> + bool need_rtnl)
> +{
> + if (need_rtnl)
> + rtnl_lock();
> +
> + netif_queue_set_napi(dev, qidx, q_type, napi);
> +
> + if (need_rtnl)
> + rtnl_unlock();
> +}
> +
> static void virtnet_napi_do_enable(struct virtqueue *vq,
> struct napi_struct *napi)
> {
> @@ -2821,15 +2835,21 @@ static void virtnet_napi_do_enable(struct virtqueue *vq,
> local_bh_enable();
> }
>
> -static void virtnet_napi_enable(struct receive_queue *rq)
> +static void virtnet_napi_enable(struct receive_queue *rq, bool need_rtnl)
> {
> + struct virtnet_info *vi = rq->vq->vdev->priv;
> + int qidx = vq2rxq(rq->vq);
> +
> virtnet_napi_do_enable(rq->vq, &rq->napi);
> + virtnet_queue_set_napi(vi->dev, &rq->napi,
> + NETDEV_QUEUE_TYPE_RX, qidx, need_rtnl);
> }
>
> -static void virtnet_napi_tx_enable(struct send_queue *sq)
> +static void virtnet_napi_tx_enable(struct send_queue *sq, bool need_rtnl)
> {
> struct virtnet_info *vi = sq->vq->vdev->priv;
> struct napi_struct *napi = &sq->napi;
> + int qidx = vq2txq(sq->vq);
>
> if (!napi->weight)
> return;
> @@ -2843,20 +2863,31 @@ static void virtnet_napi_tx_enable(struct send_queue *sq)
> }
>
> virtnet_napi_do_enable(sq->vq, napi);
> + virtnet_queue_set_napi(vi->dev, napi, NETDEV_QUEUE_TYPE_TX, qidx,
> + need_rtnl);
> }
>
> -static void virtnet_napi_tx_disable(struct send_queue *sq)
> +static void virtnet_napi_tx_disable(struct send_queue *sq, bool need_rtnl)
> {
> + struct virtnet_info *vi = sq->vq->vdev->priv;
> struct napi_struct *napi = &sq->napi;
> + int qidx = vq2txq(sq->vq);
>
> - if (napi->weight)
> + if (napi->weight) {
> + virtnet_queue_set_napi(vi->dev, NULL, NETDEV_QUEUE_TYPE_TX,
> + qidx, need_rtnl);
> napi_disable(napi);
> + }
> }
>
> -static void virtnet_napi_disable(struct receive_queue *rq)
> +static void virtnet_napi_disable(struct receive_queue *rq, bool need_rtnl)
> {
> + struct virtnet_info *vi = rq->vq->vdev->priv;
> struct napi_struct *napi = &rq->napi;
> + int qidx = vq2rxq(rq->vq);
>
> + virtnet_queue_set_napi(vi->dev, NULL, NETDEV_QUEUE_TYPE_TX, qidx,
> + need_rtnl);
> napi_disable(napi);
> }
>
> @@ -2870,9 +2901,9 @@ static void refill_work(struct work_struct *work)
> for (i = 0; i < vi->curr_queue_pairs; i++) {
> struct receive_queue *rq = &vi->rq[i];
>
> - virtnet_napi_disable(rq);
> + virtnet_napi_disable(rq, true);
> still_empty = !try_fill_recv(vi, rq, GFP_KERNEL);
> - virtnet_napi_enable(rq);
> + virtnet_napi_enable(rq, true);
>
> /* In theory, this can happen: if we don't get any buffers in
> * we will *never* try to fill again.
> @@ -3069,8 +3100,8 @@ 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]);
> - virtnet_napi_disable(&vi->rq[qp_index]);
> + virtnet_napi_tx_disable(&vi->sq[qp_index], false);
> + virtnet_napi_disable(&vi->rq[qp_index], false);
> xdp_rxq_info_unreg(&vi->rq[qp_index].xdp_rxq);
> }
>
> @@ -3089,8 +3120,8 @@ static int virtnet_enable_queue_pair(struct virtnet_info *vi, int qp_index)
> if (err < 0)
> goto err_xdp_reg_mem_model;
>
> - virtnet_napi_enable(&vi->rq[qp_index]);
> - virtnet_napi_tx_enable(&vi->sq[qp_index]);
> + virtnet_napi_enable(&vi->rq[qp_index], false);
> + virtnet_napi_tx_enable(&vi->sq[qp_index], false);
>
> return 0;
>
> @@ -3342,7 +3373,7 @@ static void virtnet_rx_pause(struct virtnet_info *vi, struct receive_queue *rq)
> bool running = netif_running(vi->dev);
>
> if (running) {
> - virtnet_napi_disable(rq);
> + virtnet_napi_disable(rq, true);
During the resize, the rtnl lock has been held on the ethtool path
rtnl_lock();
rc = __dev_ethtool(net, ifr, useraddr, ethcmd, state);
rtnl_unlock();
virtnet_rx_resize()
virtnet_rx_pause()
and in the case of XSK binding, I see ASSERT_RTNL in xp_assign_dev() at least.
Thanks
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