Re: [PATCH net-next v3 7/8] virtio-net: poll tx call xsk zerocopy xmit

From: Jason Wang <jasowang@redhat.com>
To: Xuan Zhuo <xuanzhuo@linux.alibaba.com>, netdev@vger.kernel.org
Cc: "Michael S. Tsirkin" <mst@redhat.com>,
	"David S. Miller" <davem@davemloft.net>,
	"Jakub Kicinski" <kuba@kernel.org>,
	"Björn Töpel" <bjorn@kernel.org>,
	"Magnus Karlsson" <magnus.karlsson@intel.com>,
	"Jonathan Lemon" <jonathan.lemon@gmail.com>,
	"Alexei Starovoitov" <ast@kernel.org>,
	"Daniel Borkmann" <daniel@iogearbox.net>,
	"Jesper Dangaard Brouer" <hawk@kernel.org>,
	"John Fastabend" <john.fastabend@gmail.com>,
	"Andrii Nakryiko" <andrii@kernel.org>,
	"Martin KaFai Lau" <kafai@fb.com>,
	"Song Liu" <songliubraving@fb.com>, "Yonghong Song" <yhs@fb.com>,
	"KP Singh" <kpsingh@kernel.org>,
	virtualization@lists.linux-foundation.org, bpf@vger.kernel.org,
	"Dust Li" <dust.li@linux.alibaba.com>
Subject: Re: [PATCH net-next v3 7/8] virtio-net: poll tx call xsk zerocopy xmit
Date: Tue, 6 Apr 2021 15:03:29 +0800	[thread overview]
Message-ID: <f8631a22-c51a-f5ee-7130-a3cadf1a8b25@redhat.com> (raw)
In-Reply-To: <20210331071139.15473-8-xuanzhuo@linux.alibaba.com>

在 2021/3/31 下午3:11, Xuan Zhuo 写道:
> poll tx call virtnet_xsk_run, then the data in the xsk tx queue will be
> continuously consumed by napi.
>
> Signed-off-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
> Reviewed-by: Dust Li <dust.li@linux.alibaba.com>

I think we need squash this into patch 4, it looks more like a bug fix 
to me.

> ---
>   drivers/net/virtio_net.c | 20 +++++++++++++++++---
>   1 file changed, 17 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index d7e95f55478d..fac7d0020013 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -264,6 +264,9 @@ struct padded_vnet_hdr {
>   	char padding[4];
>   };
>   
> +static int virtnet_xsk_run(struct send_queue *sq, struct xsk_buff_pool *pool,
> +			   int budget, bool in_napi);
> +
>   static bool is_xdp_frame(void *ptr)
>   {
>   	return (unsigned long)ptr & VIRTIO_XDP_FLAG;
> @@ -1553,7 +1556,9 @@ static int virtnet_poll_tx(struct napi_struct *napi, int budget)
>   	struct send_queue *sq = container_of(napi, struct send_queue, napi);
>   	struct virtnet_info *vi = sq->vq->vdev->priv;
>   	unsigned int index = vq2txq(sq->vq);
> +	struct xsk_buff_pool *pool;
>   	struct netdev_queue *txq;
> +	int work = 0;
>   
>   	if (unlikely(is_xdp_raw_buffer_queue(vi, index))) {
>   		/* We don't need to enable cb for XDP */
> @@ -1563,15 +1568,24 @@ static int virtnet_poll_tx(struct napi_struct *napi, int budget)
>   
>   	txq = netdev_get_tx_queue(vi->dev, index);
>   	__netif_tx_lock(txq, raw_smp_processor_id());
> -	free_old_xmit_skbs(sq, true);
> +	rcu_read_lock();
> +	pool = rcu_dereference(sq->xsk.pool);
> +	if (pool) {
> +		work = virtnet_xsk_run(sq, pool, budget, true);
> +		rcu_read_unlock();
> +	} else {
> +		rcu_read_unlock();
> +		free_old_xmit_skbs(sq, true);
> +	}
>   	__netif_tx_unlock(txq);
>   
> -	virtqueue_napi_complete(napi, sq->vq, 0);
> +	if (work < 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;

Need a separate patch to "fix" the budget returned by poll_tx here.

Thanks

>   }
>   
>   static int xmit_skb(struct send_queue *sq, struct sk_buff *skb)