netdev - Re: [RFC, PATCH 2/2, net-next] net: netsec: add XDP support

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Date:   Thu, 27 Jun 2019 14:23:05 +0200
From:   Jesper Dangaard Brouer <brouer@...hat.com>
To:     Ilias Apalodimas <ilias.apalodimas@...aro.org>
Cc:     netdev@...r.kernel.org, jaswinder.singh@...aro.org,
        ard.biesheuvel@...aro.org, bjorn.topel@...el.com,
        magnus.karlsson@...el.com, daniel@...earbox.net, ast@...nel.org,
        makita.toshiaki@....ntt.co.jp, jakub.kicinski@...ronome.com,
        john.fastabend@...il.com, davem@...emloft.net, brouer@...hat.com
Subject: Re: [RFC, PATCH 2/2, net-next] net: netsec: add XDP support

On Tue, 25 Jun 2019 18:06:19 +0300
Ilias Apalodimas <ilias.apalodimas@...aro.org> wrote:

> @@ -609,6 +639,9 @@ static bool netsec_clean_tx_dring(struct netsec_priv *priv)
>  	int tail = dring->tail;
>  	int cnt = 0;
>  
> +	if (dring->is_xdp)
> +		spin_lock(&dring->lock);
> +
>  	pkts = 0;
>  	bytes = 0;
>  	entry = dring->vaddr + DESC_SZ * tail;
> @@ -622,16 +655,24 @@ static bool netsec_clean_tx_dring(struct netsec_priv *priv)
>  		eop = (entry->attr >> NETSEC_TX_LAST) & 1;
>  		dma_rmb();
>  
> -		dma_unmap_single(priv->dev, desc->dma_addr, desc->len,
> -				 DMA_TO_DEVICE);
> -		if (eop) {
> -			pkts++;
> +		if (!eop)
> +			goto next;
> +
> +		if (desc->buf_type == TYPE_NETSEC_SKB) {
> +			dma_unmap_single(priv->dev, desc->dma_addr, desc->len,
> +					 DMA_TO_DEVICE);

I don't think this is correct.  If I read the code correctly, you will
miss the DMA unmap for !eop packets.

>  			bytes += desc->skb->len;
>  			dev_kfree_skb(desc->skb);
> +		} else {
> +			if (desc->buf_type == TYPE_NETSEC_XDP_NDO)
> +				dma_unmap_single(priv->dev, desc->dma_addr,
> +						 desc->len, DMA_TO_DEVICE);
> +			xdp_return_frame(desc->xdpf);
>  		}
>  		/* clean up so netsec_uninit_pkt_dring() won't free the skb
>  		 * again
>  		 */
> +next:
>  		*desc = (struct netsec_desc){};
>  
>  		/* entry->attr is not going to be accessed by the NIC until
> @@ -645,6 +686,8 @@ static bool netsec_clean_tx_dring(struct netsec_priv *priv)
>  		entry = dring->vaddr + DESC_SZ * tail;
>  		cnt++;
>  	}
> +	if (dring->is_xdp)
> +		spin_unlock(&dring->lock);
>  
>  	if (!cnt)
>  		return false;



-- 
Best regards,
  Jesper Dangaard Brouer
  MSc.CS, Principal Kernel Engineer at Red Hat
  LinkedIn: http://www.linkedin.com/in/brouer