Re: [PATCH v2 net-next 14/14] net: fec: add AF_XDP zero-copy support

[Frank Li <Frank.li@nxp.com>]

On Fri, Jan 16, 2026 at 03:40:27PM +0800, Wei Fang wrote:
> Add AF_XDP zero-copy support for both TX and RX.
>
> For RX, instead of allocating buffers from the page pool, the buffers
> are allocated from xsk pool, so fec_alloc_rxq_buffers_zc() is added to
> allocate RX buffers from xsk pool. And fec_enet_rx_queue_xsk() is used
> to process the frames from the RX queue which is bound to the AF_XDP
> socket. Similar to the XDP copy mode, the zero-copy mode also supports
> XDP_TX, XDP_PASS, XDP_DROP and XDP_REDIRECT actions. In addition,
> fec_enet_xsk_tx_xmit() is similar to fec_enet_xdp_tx_xmit() and is used
> to handle XDP_TX action in zero-copy mode.
>
> For TX, there are two cases, one is the frames from the AF_XDP socket,
> so fec_enet_xsk_xmit() is added to directly transmit the frames from
> the socket and the buffer type is marked as FEC_TXBUF_T_XSK_XMIT. The
> other one is the frams from the RX queue (XDP_TX action), the buffer
> type is marked as FEC_TXBUF_T_XSK_TX. Therefore, fec_enet_tx_queue()
> could correctly clean the TX queue base on the buffer type.
>
> Also, some tests have been done on the i.MX93-EVK board with the xdpsock
> tool, the following are the results.
>
> Env: i.MX93 connects to a packet generator, the link speed is 1Gbps, and
> flow-control is off. The RX packet size is 64 bytes including FCS. Only
> one RX queue (CPU) is used to receive frames.
>
> 1. MAC swap L2 forwarding
> 1.1 Zero-copy mode
> root@imx93evk:~# ./xdpsock -i eth0 -l -z
>  sock0@eth0:0 l2fwd xdp-drv
>                    pps            pkts           1.00
> rx                 414715         415455
> tx                 414715         415455
>
> 1.2 Copy mode
> root@imx93evk:~# ./xdpsock -i eth0 -l -c
>  sock0@eth0:0 l2fwd xdp-drv
>                    pps            pkts           1.00
> rx                 356396         356609
> tx                 356396         356609
>
> 2. TX only
> 2.1 Zero-copy mode
> root@imx93evk:~# ./xdpsock -i eth0 -t -s 64 -z
>  sock0@eth0:0 txonly xdp-drv
>                    pps            pkts           1.00
> rx                 0              0
> tx                 1119573        1126720
>
> 2.2 Copy mode
> root@imx93evk:~# ./xdpsock -i eth0 -t -s 64 -c
> sock0@eth0:0 txonly xdp-drv
>                    pps            pkts           1.00
> rx                 0              0
> tx                 406864         407616
>
> Signed-off-by: Wei Fang <wei.fang@nxp.com>
> ---
>  drivers/net/ethernet/freescale/fec.h      |  13 +-
>  drivers/net/ethernet/freescale/fec_main.c | 611 ++++++++++++++++++++--
>  2 files changed, 582 insertions(+), 42 deletions(-)
>
> diff --git a/drivers/net/ethernet/freescale/fec.h b/drivers/net/ethernet/freescale/fec.h
> index ad7aba1a8536..7176803146f3 100644
> --- a/drivers/net/ethernet/freescale/fec.h
> +++ b/drivers/net/ethernet/freescale/fec.h
...
>  static int fec_enet_bpf(struct net_device *dev, struct netdev_bpf *bpf)
>  {
>  	struct fec_enet_private *fep = netdev_priv(dev);
>  	bool is_run = netif_running(dev);
>  	struct bpf_prog *old_prog;
>
> +	/* No need to support the SoCs that require to do the frame swap
> +	 * because the performance wouldn't be better than the skb mode.
> +	 */
> +	if (fep->quirks & FEC_QUIRK_SWAP_FRAME)
> +		return -EOPNOTSUPP;
> +
>  	switch (bpf->command) {
>  	case XDP_SETUP_PROG:
> -		/* No need to support the SoCs that require to
> -		 * do the frame swap because the performance wouldn't be
> -		 * better than the skb mode.
> -		 */
> -		if (fep->quirks & FEC_QUIRK_SWAP_FRAME)
> -			return -EOPNOTSUPP;
> -

This part can be new patch.

Code itself look good, but I am not familar XDP's logic.

Frank

>  		if (!bpf->prog)
>  			xdp_features_clear_redirect_target(dev);
>
> @@ -3994,7 +4497,8 @@ static int fec_enet_bpf(struct net_device *dev, struct netdev_bpf *bpf)
>  		return 0;
>
>  	case XDP_SETUP_XSK_POOL:
> -		return -EOPNOTSUPP;
> +		return fec_setup_xsk_pool(dev, bpf->xsk.pool,
> +					  bpf->xsk.queue_id);
>
>  	default:
>  		return -EOPNOTSUPP;
> @@ -4143,6 +4647,29 @@ static int fec_enet_xdp_xmit(struct net_device *dev,
>  	return sent_frames;
>  }
>
> +static int fec_enet_xsk_wakeup(struct net_device *ndev, u32 queue, u32 flags)
> +{
> +	struct fec_enet_private *fep = netdev_priv(ndev);
> +	struct fec_enet_priv_rx_q *rxq;
> +
> +	if (!netif_running(ndev) || !netif_carrier_ok(ndev))
> +		return -ENETDOWN;
> +
> +	if (queue >= fep->num_rx_queues || queue >= fep->num_tx_queues)
> +		return -ERANGE;
> +
> +	rxq = fep->rx_queue[queue];
> +	if (!rxq->xsk_pool)
> +		return -EINVAL;
> +
> +	if (!napi_if_scheduled_mark_missed(&fep->napi)) {
> +		if (likely(napi_schedule_prep(&fep->napi)))
> +			__napi_schedule(&fep->napi);
> +	}
> +
> +	return 0;
> +}
> +
>  static int fec_hwtstamp_get(struct net_device *ndev,
>  			    struct kernel_hwtstamp_config *config)
>  {
> @@ -4205,6 +4732,7 @@ static const struct net_device_ops fec_netdev_ops = {
>  	.ndo_set_features	= fec_set_features,
>  	.ndo_bpf		= fec_enet_bpf,
>  	.ndo_xdp_xmit		= fec_enet_xdp_xmit,
> +	.ndo_xsk_wakeup		= fec_enet_xsk_wakeup,
>  	.ndo_hwtstamp_get	= fec_hwtstamp_get,
>  	.ndo_hwtstamp_set	= fec_hwtstamp_set,
>  };
> @@ -4332,7 +4860,8 @@ static int fec_enet_init(struct net_device *ndev)
>
>  	if (!(fep->quirks & FEC_QUIRK_SWAP_FRAME))
>  		ndev->xdp_features = NETDEV_XDP_ACT_BASIC |
> -				     NETDEV_XDP_ACT_REDIRECT;
> +				     NETDEV_XDP_ACT_REDIRECT |
> +				     NETDEV_XDP_ACT_XSK_ZEROCOPY;
>
>  	fec_restart(ndev);
>
> --
> 2.34.1
>