linux-kernel - Re: [PATCH 1/1] net: fec: enable the XDP

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Date:   Tue, 2 May 2023 22:31:17 +0200
From:   Horatiu Vultur <horatiu.vultur@...rochip.com>
To:     Shenwei Wang <shenwei.wang@....com>
CC:     Wei Fang <wei.fang@....com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Clark Wang <xiaoning.wang@....com>,
        NXP Linux Team <linux-imx@....com>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Jesper Dangaard Brouer <hawk@...nel.org>,
        John Fastabend <john.fastabend@...il.com>,
        Alexander Lobakin <alexandr.lobakin@...el.com>,
        <netdev@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <imx@...ts.linux.dev>, Gagandeep Singh <g.singh@....com>
Subject: Re: [PATCH 1/1] net: fec: enable the XDP_TX support

The 05/02/2023 14:32, Shenwei Wang wrote:

Hi Shenwei,

> 
> Enable the XDP_TX path and correct the return value of the xmit function.

I think this patch should be split in 2. One that adds support for
XDP_TX which needs to go in net-next, and one where you fix the
return value of the function 'fec_enect_xdp_xmit' which needs to
go in net.
Other than that it looks fine, just a small comment bellow.

> 
> If any individual frame cannot transmit due to lack of BD entries, the
> function would still return success for sending all frames. This results
> in prematurely indicating frames were sent when they were actually dropped.
> 
> The patch resolves the issue by ensureing the return value properly
> indicates the actual number of frames successfully transmitted, rather than
> potentially reporting success for all frames when some could not transmit.
> 
> Fixes: 6d6b39f180b8 ("net: fec: add initial XDP support")
> Signed-off-by: Gagandeep Singh <g.singh@....com>
> Signed-off-by: Shenwei Wang <shenwei.wang@....com>
> ---
>  drivers/net/ethernet/freescale/fec_main.c | 27 ++++++++++++++++-------
>  1 file changed, 19 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/net/ethernet/freescale/fec_main.c b/drivers/net/ethernet/freescale/fec_main.c
> index 160c1b3525f5..dfc1bcc9a8db 100644
> --- a/drivers/net/ethernet/freescale/fec_main.c
> +++ b/drivers/net/ethernet/freescale/fec_main.c
> @@ -75,6 +75,10 @@
> 
>  static void set_multicast_list(struct net_device *ndev);
>  static void fec_enet_itr_coal_set(struct net_device *ndev);
> +static int fec_enet_xdp_xmit(struct net_device *dev,
> +                            int num_frames,
> +                            struct xdp_frame **frames,
> +                            u32 flags);

Sometimes, I received comments at my patches not to have forward
declaration of the functions.

> 
>  #define DRIVER_NAME    "fec"
> 
> @@ -1517,6 +1521,7 @@ fec_enet_run_xdp(struct fec_enet_private *fep, struct bpf_prog *prog,
>  {
>         unsigned int sync, len = xdp->data_end - xdp->data;
>         u32 ret = FEC_ENET_XDP_PASS;
> +       struct xdp_frame *xdp_frame;
>         struct page *page;
>         int err;
>         u32 act;
> @@ -1545,11 +1550,12 @@ fec_enet_run_xdp(struct fec_enet_private *fep, struct bpf_prog *prog,
>                 }
>                 break;
> 
> -       default:
> -               bpf_warn_invalid_xdp_action(fep->netdev, prog, act);
> -               fallthrough;
> -
>         case XDP_TX:
> +               xdp_frame = xdp_convert_buff_to_frame(xdp);
> +               ret = fec_enet_xdp_xmit(fep->netdev, 1, &xdp_frame, 0);
> +               break;
> +
> +       default:
>                 bpf_warn_invalid_xdp_action(fep->netdev, prog, act);
>                 fallthrough;
> 
> @@ -3798,7 +3804,8 @@ static int fec_enet_txq_xmit_frame(struct fec_enet_private *fep,
>         entries_free = fec_enet_get_free_txdesc_num(txq);
>         if (entries_free < MAX_SKB_FRAGS + 1) {
>                 netdev_err(fep->netdev, "NOT enough BD for SG!\n");
> -               return NETDEV_TX_OK;
> +               xdp_return_frame(frame);
> 
>         struct fec_enet_private *fep = netdev_priv(dev);
>         struct fec_enet_priv_tx_q *txq;
>         int cpu = smp_processor_id();
> +       unsigned int sent_frames = 0;
>         struct netdev_queue *nq;
>         unsigned int queue;
>         int i;
> @@ -3866,8 +3874,11 @@ static int fec_enet_xdp_xmit(struct net_device *dev,
> 
>         __netif_tx_lock(nq, cpu);
> 
> -       for (i = 0; i < num_frames; i++)
> -               fec_enet_txq_xmit_frame(fep, txq, frames[i]);
> +       for (i = 0; i < num_frames; i++) {
> +               if (fec_enet_txq_xmit_frame(fep, txq, frames[i]) != 0)
> +                       break;
> +               sent_frames++;
> +       }
> 
>         /* Make sure the update to bdp and tx_skbuff are performed. */
>         wmb();
> @@ -3877,7 +3888,7 @@ static int fec_enet_xdp_xmit(struct net_device *dev,
> 
>         __netif_tx_unlock(nq);
> 
> -       return num_frames;
> +       return sent_frames;
>  }
> 
>  static const struct net_device_ops fec_netdev_ops = {
> --
> 2.34.1
> 

-- 
/Horatiu