netdev - Re: [net PATCH v5 3/6] virtio_net: factor out xdp handler for readability

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Date:   Wed, 18 Jan 2017 17:48:57 +0200
From:   "Michael S. Tsirkin" <mst@...hat.com>
To:     John Fastabend <john.fastabend@...il.com>
Cc:     jasowang@...hat.com, john.r.fastabend@...el.com,
        netdev@...r.kernel.org, alexei.starovoitov@...il.com,
        daniel@...earbox.net
Subject: Re: [net PATCH v5 3/6] virtio_net: factor out xdp handler for
 readability

On Tue, Jan 17, 2017 at 02:21:07PM -0800, John Fastabend wrote:
> At this point the do_xdp_prog is mostly if/else branches handling
> the different modes of virtio_net. So remove it and handle running
> the program in the per mode handlers.
> 
> Signed-off-by: John Fastabend <john.r.fastabend@...el.com>

Acked-by: Michael S. Tsirkin <mst@...hat.com>

> ---
>  drivers/net/virtio_net.c |   75 +++++++++++++++++-----------------------------
>  1 file changed, 27 insertions(+), 48 deletions(-)
> 
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index ba0efee..6de0cbe 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -388,49 +388,6 @@ static void virtnet_xdp_xmit(struct virtnet_info *vi,
>  	virtqueue_kick(sq->vq);
>  }
>  
> -static u32 do_xdp_prog(struct virtnet_info *vi,
> -		       struct receive_queue *rq,
> -		       struct bpf_prog *xdp_prog,
> -		       void *data, int len)
> -{
> -	int hdr_padded_len;
> -	struct xdp_buff xdp;
> -	void *buf;
> -	unsigned int qp;
> -	u32 act;
> -
> -	if (vi->mergeable_rx_bufs) {
> -		hdr_padded_len = sizeof(struct virtio_net_hdr_mrg_rxbuf);
> -		xdp.data = data + hdr_padded_len;
> -		xdp.data_end = xdp.data + (len - vi->hdr_len);
> -		buf = data;
> -	} else { /* small buffers */
> -		struct sk_buff *skb = data;
> -
> -		xdp.data = skb->data;
> -		xdp.data_end = xdp.data + len;
> -		buf = skb->data;
> -	}
> -
> -	act = bpf_prog_run_xdp(xdp_prog, &xdp);
> -	switch (act) {
> -	case XDP_PASS:
> -		return XDP_PASS;
> -	case XDP_TX:
> -		qp = vi->curr_queue_pairs -
> -			vi->xdp_queue_pairs +
> -			smp_processor_id();
> -		xdp.data = buf;
> -		virtnet_xdp_xmit(vi, rq, &vi->sq[qp], &xdp, data);
> -		return XDP_TX;
> -	default:
> -		bpf_warn_invalid_xdp_action(act);
> -	case XDP_ABORTED:
> -	case XDP_DROP:
> -		return XDP_DROP;
> -	}
> -}
> -
>  static struct sk_buff *receive_small(struct net_device *dev,
>  				     struct virtnet_info *vi,
>  				     struct receive_queue *rq,
> @@ -446,19 +403,30 @@ static struct sk_buff *receive_small(struct net_device *dev,
>  	xdp_prog = rcu_dereference(rq->xdp_prog);
>  	if (xdp_prog) {
>  		struct virtio_net_hdr_mrg_rxbuf *hdr = buf;
> +		struct xdp_buff xdp;
> +		unsigned int qp;
>  		u32 act;
>  
>  		if (unlikely(hdr->hdr.gso_type || hdr->hdr.flags))
>  			goto err_xdp;
> -		act = do_xdp_prog(vi, rq, xdp_prog, skb, len);
> +
> +		xdp.data = skb->data;
> +		xdp.data_end = xdp.data + len;
> +		act = bpf_prog_run_xdp(xdp_prog, &xdp);
>  		switch (act) {
>  		case XDP_PASS:
>  			break;
>  		case XDP_TX:
> +			qp = vi->curr_queue_pairs -
> +				vi->xdp_queue_pairs +
> +				smp_processor_id();
> +			virtnet_xdp_xmit(vi, rq, &vi->sq[qp], &xdp, skb);
>  			rcu_read_unlock();
>  			goto xdp_xmit;
> -		case XDP_DROP:
>  		default:
> +			bpf_warn_invalid_xdp_action(act);
> +		case XDP_ABORTED:
> +		case XDP_DROP:
>  			goto err_xdp;
>  		}
>  	}
> @@ -576,6 +544,9 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
>  	xdp_prog = rcu_dereference(rq->xdp_prog);
>  	if (xdp_prog) {
>  		struct page *xdp_page;
> +		struct xdp_buff xdp;
> +		unsigned int qp;
> +		void *data;
>  		u32 act;
>  
>  		/* This happens when rx buffer size is underestimated */
> @@ -598,8 +569,10 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
>  		if (unlikely(hdr->hdr.gso_type))
>  			goto err_xdp;
>  
> -		act = do_xdp_prog(vi, rq, xdp_prog,
> -				  page_address(xdp_page) + offset, len);
> +		data = page_address(xdp_page) + offset;
> +		xdp.data = data + vi->hdr_len;
> +		xdp.data_end = xdp.data + (len - vi->hdr_len);
> +		act = bpf_prog_run_xdp(xdp_prog, &xdp);
>  		switch (act) {
>  		case XDP_PASS:
>  			/* We can only create skb based on xdp_page. */
> @@ -613,13 +586,19 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
>  			}
>  			break;
>  		case XDP_TX:
> +			qp = vi->curr_queue_pairs -
> +				vi->xdp_queue_pairs +
> +				smp_processor_id();
> +			virtnet_xdp_xmit(vi, rq, &vi->sq[qp], &xdp, data);
>  			ewma_pkt_len_add(&rq->mrg_avg_pkt_len, len);
>  			if (unlikely(xdp_page != page))
>  				goto err_xdp;
>  			rcu_read_unlock();
>  			goto xdp_xmit;
> -		case XDP_DROP:
>  		default:
> +			bpf_warn_invalid_xdp_action(act);
> +		case XDP_ABORTED:
> +		case XDP_DROP:
>  			if (unlikely(xdp_page != page))
>  				__free_pages(xdp_page, 0);
>  			ewma_pkt_len_add(&rq->mrg_avg_pkt_len, len);