netdev - Re: [PATCH v2 net-next 10/11] qede: Add basic XDP support

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Message-ID: <583DA362.7010702@iogearbox.net>
Date:   Tue, 29 Nov 2016 16:48:50 +0100
From:   Daniel Borkmann <daniel@...earbox.net>
To:     Yuval Mintz <Yuval.Mintz@...ium.com>
CC:     davem@...emloft.net, netdev@...r.kernel.org,
        alexei.starovoitov@...il.com
Subject: Re: [PATCH v2 net-next 10/11] qede: Add basic XDP support

On 11/29/2016 03:47 PM, Yuval Mintz wrote:
> Add support for the ndo_xdp callback. This patch would support XDP_PASS,
> XDP_DROP and XDP_ABORTED commands.
>
> This also adds a per Rx queue statistic which counts number of packets
> which didn't reach the stack [due to XDP].
>
> Signed-off-by: Yuval Mintz <Yuval.Mintz@...ium.com>
[...]
> @@ -1560,6 +1593,7 @@ static int qede_rx_process_cqe(struct qede_dev *edev,
>   			       struct qede_fastpath *fp,
>   			       struct qede_rx_queue *rxq)
>   {
> +	struct bpf_prog *xdp_prog = READ_ONCE(rxq->xdp_prog);
>   	struct eth_fast_path_rx_reg_cqe *fp_cqe;
>   	u16 len, pad, bd_cons_idx, parse_flag;
>   	enum eth_rx_cqe_type cqe_type;
> @@ -1596,6 +1630,11 @@ static int qede_rx_process_cqe(struct qede_dev *edev,
>   	len = le16_to_cpu(fp_cqe->len_on_first_bd);
>   	pad = fp_cqe->placement_offset;
>
> +	/* Run eBPF program if one is attached */
> +	if (xdp_prog)
> +		if (!qede_rx_xdp(edev, fp, rxq, xdp_prog, bd, fp_cqe))
> +			return 1;
> +

You also need to wrap this under rcu_read_lock() (at least I haven't seen
it in your patches) for same reasons as stated in 326fe02d1ed6 ("net/mlx4_en:
protect ring->xdp_prog with rcu_read_lock"), as otherwise xdp_prog could
disappear underneath you. mlx4 and nfp does it correctly, looks like mlx5
doesn't.