netdev - Re: [PATCH net-next 15/16] idpf: add support for .ndo_xdp

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Message-ID: <Z9Bf9o+t4BmFsMQG@boxer>
Date: Tue, 11 Mar 2025 17:08:22 +0100
From: Maciej Fijalkowski <maciej.fijalkowski@...el.com>
To: Alexander Lobakin <aleksander.lobakin@...el.com>
CC: <intel-wired-lan@...ts.osuosl.org>, Michal Kubiak
	<michal.kubiak@...el.com>, Tony Nguyen <anthony.l.nguyen@...el.com>, "Przemek
 Kitszel" <przemyslaw.kitszel@...el.com>, Andrew Lunn <andrew+netdev@...n.ch>,
	"David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, "Alexei
 Starovoitov" <ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net>,
	"Jesper Dangaard Brouer" <hawk@...nel.org>, John Fastabend
	<john.fastabend@...il.com>, Simon Horman <horms@...nel.org>,
	<bpf@...r.kernel.org>, <netdev@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH net-next 15/16] idpf: add support for .ndo_xdp_xmit()

On Wed, Mar 05, 2025 at 05:21:31PM +0100, Alexander Lobakin wrote:
> Use libeth XDP infra to implement .ndo_xdp_xmit() in idpf.
> The Tx callbacks are reused from XDP_TX code. XDP redirect target
> feature is set/cleared depending on the XDP prog presence, as for now
> we still don't allocate XDP Tx queues when there's no program.
> 
> Signed-off-by: Alexander Lobakin <aleksander.lobakin@...el.com>
> ---
>  drivers/net/ethernet/intel/idpf/xdp.h      |  2 ++
>  drivers/net/ethernet/intel/idpf/idpf_lib.c |  1 +
>  drivers/net/ethernet/intel/idpf/xdp.c      | 29 ++++++++++++++++++++++
>  3 files changed, 32 insertions(+)
> 
> diff --git a/drivers/net/ethernet/intel/idpf/xdp.h b/drivers/net/ethernet/intel/idpf/xdp.h
> index fde85528a315..a2ac1b2f334f 100644
> --- a/drivers/net/ethernet/intel/idpf/xdp.h
> +++ b/drivers/net/ethernet/intel/idpf/xdp.h
> @@ -110,5 +110,7 @@ static inline void idpf_xdp_tx_finalize(void *_xdpq, bool sent, bool flush)
>  void idpf_xdp_set_features(const struct idpf_vport *vport);
>  
>  int idpf_xdp(struct net_device *dev, struct netdev_bpf *xdp);
> +int idpf_xdp_xmit(struct net_device *dev, int n, struct xdp_frame **frames,
> +		  u32 flags);
>  
>  #endif /* _IDPF_XDP_H_ */
> diff --git a/drivers/net/ethernet/intel/idpf/idpf_lib.c b/drivers/net/ethernet/intel/idpf/idpf_lib.c
> index 2d1efcb854be..39b9885293a9 100644
> --- a/drivers/net/ethernet/intel/idpf/idpf_lib.c
> +++ b/drivers/net/ethernet/intel/idpf/idpf_lib.c
> @@ -2371,4 +2371,5 @@ static const struct net_device_ops idpf_netdev_ops = {
>  	.ndo_set_features = idpf_set_features,
>  	.ndo_tx_timeout = idpf_tx_timeout,
>  	.ndo_bpf = idpf_xdp,
> +	.ndo_xdp_xmit = idpf_xdp_xmit,
>  };
> diff --git a/drivers/net/ethernet/intel/idpf/xdp.c b/drivers/net/ethernet/intel/idpf/xdp.c
> index abf75e840c0a..1834f217a07f 100644
> --- a/drivers/net/ethernet/intel/idpf/xdp.c
> +++ b/drivers/net/ethernet/intel/idpf/xdp.c
> @@ -357,8 +357,35 @@ LIBETH_XDP_DEFINE_START();
>  LIBETH_XDP_DEFINE_TIMER(static idpf_xdp_tx_timer, idpf_clean_xdp_irq);
>  LIBETH_XDP_DEFINE_FLUSH_TX(idpf_xdp_tx_flush_bulk, idpf_xdp_tx_prep,
>  			   idpf_xdp_tx_xmit);
> +LIBETH_XDP_DEFINE_FLUSH_XMIT(static idpf_xdp_xmit_flush_bulk, idpf_xdp_tx_prep,
> +			     idpf_xdp_tx_xmit);
>  LIBETH_XDP_DEFINE_END();
>  
> +/**
> + * idpf_xdp_xmit - send frames queued by ``XDP_REDIRECT`` to this interface
> + * @dev: network device
> + * @n: number of frames to transmit
> + * @frames: frames to transmit
> + * @flags: transmit flags (``XDP_XMIT_FLUSH`` or zero)
> + *
> + * Return: number of frames successfully sent or -errno on error.
> + */
> +int idpf_xdp_xmit(struct net_device *dev, int n, struct xdp_frame **frames,
> +		  u32 flags)
> +{
> +	const struct idpf_netdev_priv *np = netdev_priv(dev);
> +	const struct idpf_vport *vport = np->vport;
> +
> +	if (unlikely(!netif_carrier_ok(dev) || !vport->link_up))
> +		return -ENETDOWN;
> +
> +	return libeth_xdp_xmit_do_bulk(dev, n, frames, flags,
> +				       &vport->txqs[vport->xdp_txq_offset],
> +				       vport->num_xdp_txq,

Have you considered in some future libeth being stateful where you could
provide some initialization data such as vport->num_xdp_txq which is
rather constant so that we wouldn't have to pass this all the time?

I got a bit puzzled here as it took me some digging that it is only used a
bound check and libeth_xdpsq_id() uses cpu id as an index.

Reviewed-by: Maciej Fijalkowski <maciej.fijalkowski@...el.com>

> +				       idpf_xdp_xmit_flush_bulk,
> +				       idpf_xdp_tx_finalize);
> +}
> +
>  void idpf_xdp_set_features(const struct idpf_vport *vport)
>  {
>  	if (!idpf_is_queue_model_split(vport->rxq_model))
> @@ -417,6 +444,8 @@ idpf_xdp_setup_prog(struct idpf_vport *vport, const struct netdev_bpf *xdp)
>  		cfg->user_config.xdp_prog = old;
>  	}
>  
> +	libeth_xdp_set_redirect(vport->netdev, vport->xdp_prog);
> +
>  	return ret;
>  }
>  
> -- 
> 2.48.1
>