netdev - Re: [PATCH 19/33] virtio_net: introduce virtnet_tx

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Date:   Thu, 2 Feb 2023 12:23:56 -0500
From:   "Michael S. Tsirkin" <mst@...hat.com>
To:     Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
Cc:     netdev@...r.kernel.org, "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Jason Wang <jasowang@...hat.com>,
        Björn Töpel <bjorn@...nel.org>,
        Magnus Karlsson <magnus.karlsson@...el.com>,
        Maciej Fijalkowski <maciej.fijalkowski@...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>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Menglong Dong <imagedong@...cent.com>,
        Kuniyuki Iwashima <kuniyu@...zon.com>,
        Petr Machata <petrm@...dia.com>,
        virtualization@...ts.linux-foundation.org, bpf@...r.kernel.org
Subject: Re: [PATCH 19/33] virtio_net: introduce virtnet_tx_reset()

On Thu, Feb 02, 2023 at 07:00:44PM +0800, Xuan Zhuo wrote:
> Introduce virtnet_tx_reset() to release the buffers inside virtio ring.
> 
> This is needed for xsk disable. When disable xsk, we need to relese the

typo

> buffer from xsk, so this function is needed.
> 
> This patch reuse the virtnet_tx_resize.

reuses

> Signed-off-by: Xuan Zhuo <xuanzhuo@...ux.alibaba.com>


> ---
>  drivers/net/virtio/main.c       | 21 ++++++++++++++++++---
>  drivers/net/virtio/virtio_net.h |  1 +
>  2 files changed, 19 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/net/virtio/main.c b/drivers/net/virtio/main.c
> index fb82035a0b7f..049a3bb9d88d 100644
> --- a/drivers/net/virtio/main.c
> +++ b/drivers/net/virtio/main.c
> @@ -1806,8 +1806,8 @@ static int virtnet_rx_resize(struct virtnet_info *vi,
>  	return err;
>  }
>  
> -static int virtnet_tx_resize(struct virtnet_info *vi,
> -			     struct send_queue *sq, u32 ring_num)
> +static int __virtnet_tx_reset(struct virtnet_info *vi,
> +			      struct send_queue *sq, u32 ring_num)
>  {
>  	bool running = netif_running(vi->dev);
>  	struct netdev_queue *txq;
> @@ -1833,7 +1833,11 @@ static int virtnet_tx_resize(struct virtnet_info *vi,
>  
>  	__netif_tx_unlock_bh(txq);
>  
> -	err = virtqueue_resize(sq->vq, ring_num, virtnet_sq_free_unused_buf);
> +	if (ring_num)
> +		err = virtqueue_resize(sq->vq, ring_num, virtnet_sq_free_unused_buf);
> +	else
> +		err = virtqueue_reset(sq->vq, virtnet_sq_free_unused_buf);
> +
>  	if (err)
>  		netdev_err(vi->dev, "resize tx fail: tx queue index: %d err: %d\n", qindex, err);
>

This __virtnet_tx_reset is a really weird API.

Suggest just splitting the common parts:

__virtnet_tx_pause
__virtnet_tx_resume

we can then implement virtnet_tx_resize and virtnet_tx_reset
using these two.

  
> @@ -1847,6 +1851,17 @@ static int virtnet_tx_resize(struct virtnet_info *vi,
>  	return err;
>  }
>  
> +static int virtnet_tx_resize(struct virtnet_info *vi,
> +			     struct send_queue *sq, u32 ring_num)
> +{
> +	return __virtnet_tx_reset(vi, sq, ring_num);
> +}
> +
> +int virtnet_tx_reset(struct virtnet_info *vi, struct send_queue *sq)
> +{
> +	return __virtnet_tx_reset(vi, sq, 0);
> +}
> +
>  /*
>   * Send command via the control virtqueue and check status.  Commands
>   * supported by the hypervisor, as indicated by feature bits, should
> diff --git a/drivers/net/virtio/virtio_net.h b/drivers/net/virtio/virtio_net.h
> index af3e7e817f9e..b46f083a630a 100644
> --- a/drivers/net/virtio/virtio_net.h
> +++ b/drivers/net/virtio/virtio_net.h
> @@ -273,4 +273,5 @@ int virtnet_xdp_handler(struct bpf_prog *xdp_prog, struct xdp_buff *xdp,
>  			struct net_device *dev,
>  			unsigned int *xdp_xmit,
>  			struct virtnet_rq_stats *stats);
> +int virtnet_tx_reset(struct virtnet_info *vi, struct send_queue *sq);
>  #endif
> -- 
> 2.32.0.3.g01195cf9f