netdev - Re: [net-next, PATCH 2/2, v1] net: socionext: add AF

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Message-ID: <8bfd8219-acea-8b63-b6be-d17a7e3b6e24@lab.ntt.co.jp>
Date:   Mon, 10 Sep 2018 19:56:49 +0900
From:   Toshiaki Makita <makita.toshiaki@....ntt.co.jp>
To:     Ilias Apalodimas <ilias.apalodimas@...aro.org>,
        netdev@...r.kernel.org, jaswinder.singh@...aro.org
Cc:     ard.biesheuvel@...aro.org, masami.hiramatsu@...aro.org,
        arnd@...db.de, mykyta.iziumtsev@...aro.org, bjorn.topel@...el.com,
        magnus.karlsson@...el.com
Subject: Re: [net-next, PATCH 2/2, v1] net: socionext: add AF_XDP support

On 2018/09/10 17:24, Ilias Apalodimas wrote:
> Add basic AF_XDP support without zero-copy
> 
> Signed-off-by: Ilias Apalodimas <ilias.apalodimas@...aro.org>
> ---
...
> @@ -707,6 +731,26 @@ static int netsec_process_rx(struct netsec_priv *priv, int budget)
>  		if (unlikely(!buf_addr))
>  			break;
>  
> +		if (xdp_prog) {
> +			xdp_result = netsec_run_xdp(desc, priv, xdp_prog,
> +						    pkt_len);
> +			if (xdp_result != NETSEC_XDP_PASS) {
> +				xdp_flush |= xdp_result & NETSEC_XDP_REDIR;
> +
> +				dma_unmap_single_attrs(priv->dev,
> +						       desc->dma_addr,
> +						       desc->len, DMA_TO_DEVICE,
> +						       DMA_ATTR_SKIP_CPU_SYNC);
> +
> +				desc->len = desc_len;
> +				desc->dma_addr = dma_handle;
> +				desc->addr = buf_addr;
> +				netsec_rx_fill(priv, idx, 1);
> +				nsetsec_adv_desc(&dring->tail);
> +			}
> +			continue;

Continue even on XDP_PASS? Is this really correct?

Also seems there is no handling of adjust_head/tail for XDP_PASS case.

> +		}
> +
>  		skb = build_skb(desc->addr, desc->len);
>  		if (unlikely(!skb)) {
>  			dma_unmap_single(priv->dev, dma_handle, desc_len,
> @@ -740,6 +784,9 @@ static int netsec_process_rx(struct netsec_priv *priv, int budget)
>  		nsetsec_adv_desc(&dring->tail);
>  	}
>  
> +	if (xdp_flush & NETSEC_XDP_REDIR)
> +		xdp_do_flush_map();
> +
>  	return done;
>  }
...
> +static u32 netsec_run_xdp(struct netsec_desc *desc, struct netsec_priv *priv,
> +			  struct bpf_prog *prog, u16 len)
> +
> +{
> +	struct netsec_desc_ring *dring = &priv->desc_ring[NETSEC_RING_RX];
> +	struct xdp_buff xdp;
> +	u32 ret = NETSEC_XDP_PASS;
> +	int err;
> +	u32 act;
> +
> +	xdp.data_hard_start = desc->addr;
> +	xdp.data = desc->addr;

There is no headroom. REDIRECT using devmap/cpumap will fail due to
this. Generally we need XDP_PACKET_HEADROOM.

> +	xdp_set_data_meta_invalid(&xdp);
> +	xdp.data_end = xdp.data + len;
> +	xdp.rxq = &dring->xdp_rxq;
> +
> +	rcu_read_lock();
> +	act = bpf_prog_run_xdp(prog, &xdp);
> +
> +	switch (act) {
> +	case XDP_PASS:
> +		ret = NETSEC_XDP_PASS;
> +		break;
> +	case XDP_TX:
> +		ret = netsec_xmit_xdp(priv, &xdp, desc);
> +		break;
> +	case XDP_REDIRECT:
> +		err = xdp_do_redirect(priv->ndev, &xdp, prog);
> +		if (!err) {
> +			ret = NETSEC_XDP_REDIR;
> +		} else {
> +			ret = NETSEC_XDP_CONSUMED;
> +			xdp_return_buff(&xdp);
> +		}
> +		break;
> +	default:
> +		bpf_warn_invalid_xdp_action(act);
> +		/* fall through */
> +	case XDP_ABORTED:
> +		trace_xdp_exception(priv->ndev, prog, act);
> +		/* fall through -- handle aborts by dropping packet */
> +	case XDP_DROP:
> +		ret = NETSEC_XDP_CONSUMED;
> +		break;
> +	}
> +
> +	rcu_read_unlock();
> +
> +	return ret;
> +}
> +
> +static int netsec_xdp_setup(struct netsec_priv *priv, struct bpf_prog *prog)
> +{
> +	struct net_device *dev = priv->ndev;
> +	struct bpf_prog *old_prog;
> +
> +	/* For now just support only the usual MTU sized frames */
> +	if (prog && dev->mtu > 1500) {
> +		netdev_warn(dev, "Jumbo frames not yet supported with XDP\n");

Why not using extack?

> +		return -EOPNOTSUPP;
> +	}
> +

-- 
Toshiaki Makita