Message-ID: <Z9Bbr9b0WLFQZt4Z@boxer>
Date: Tue, 11 Mar 2025 16:50:07 +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 14/16] idpf: add support for XDP on Rx

On Wed, Mar 05, 2025 at 05:21:30PM +0100, Alexander Lobakin wrote:
> Use libeth XDP infra to support running XDP program on Rx polling.
> This includes all of the possible verdicts/actions.
> XDP Tx queues are cleaned only in "lazy" mode when there are less than
> 1/4 free descriptors left on the ring. libeth helper macros to define
> driver-specific XDP functions make sure the compiler could uninline
> them when needed.
> Use __LIBETH_WORD_ACCESS to parse descriptors more efficiently when
> applicable. It really gives some good boosts and code size reduction
> on x86_64.
> 
> Co-developed-by: Michal Kubiak <michal.kubiak@...el.com>
> Signed-off-by: Michal Kubiak <michal.kubiak@...el.com>
> Signed-off-by: Alexander Lobakin <aleksander.lobakin@...el.com>
> ---
>  drivers/net/ethernet/intel/idpf/idpf_txrx.h |   4 +-
>  drivers/net/ethernet/intel/idpf/xdp.h       | 100 ++++++++++++-
>  drivers/net/ethernet/intel/idpf/idpf_lib.c  |   2 +
>  drivers/net/ethernet/intel/idpf/idpf_txrx.c |  23 +--
>  drivers/net/ethernet/intel/idpf/xdp.c       | 155 +++++++++++++++++++-
>  5 files changed, 264 insertions(+), 20 deletions(-)
> 
> diff --git a/drivers/net/ethernet/intel/idpf/idpf_txrx.h b/drivers/net/ethernet/intel/idpf/idpf_txrx.h
> index e36c55baf23f..5d62074c94b1 100644
> --- a/drivers/net/ethernet/intel/idpf/idpf_txrx.h
> +++ b/drivers/net/ethernet/intel/idpf/idpf_txrx.h
> @@ -684,8 +684,8 @@ struct idpf_tx_queue {
>  	__cacheline_group_end_aligned(read_mostly);
>  
>  	__cacheline_group_begin_aligned(read_write);
> -	u16 next_to_use;
> -	u16 next_to_clean;
> +	u32 next_to_use;
> +	u32 next_to_clean;
>  
>  	union {
>  		struct {
> diff --git a/drivers/net/ethernet/intel/idpf/xdp.h b/drivers/net/ethernet/intel/idpf/xdp.h
> index a72a7638a6ea..fde85528a315 100644
> --- a/drivers/net/ethernet/intel/idpf/xdp.h
> +++ b/drivers/net/ethernet/intel/idpf/xdp.h
> @@ -4,12 +4,9 @@
>  #ifndef _IDPF_XDP_H_
>  #define _IDPF_XDP_H_
>  
> -#include <linux/types.h>
> +#include <net/libeth/xdp.h>
>  
> -struct bpf_prog;
> -struct idpf_vport;
> -struct net_device;
> -struct netdev_bpf;
> +#include "idpf_txrx.h"
>  
>  int idpf_xdp_rxq_info_init_all(const struct idpf_vport *vport);
>  void idpf_xdp_rxq_info_deinit_all(const struct idpf_vport *vport);
> @@ -19,6 +16,99 @@ void idpf_copy_xdp_prog_to_qs(const struct idpf_vport *vport,
>  int idpf_vport_xdpq_get(const struct idpf_vport *vport);
>  void idpf_vport_xdpq_put(const struct idpf_vport *vport);
>  
> +bool idpf_xdp_tx_flush_bulk(struct libeth_xdp_tx_bulk *bq, u32 flags);
> +
> +/**
> + * idpf_xdp_tx_xmit - produce a single HW Tx descriptor out of XDP desc
> + * @desc: XDP descriptor to pull the DMA address and length from
> + * @i: descriptor index on the queue to fill
> + * @sq: XDP queue to produce the HW Tx descriptor on
> + * @priv: &xsk_tx_metadata_ops on XSk xmit or %NULL
> + */
> +static inline void idpf_xdp_tx_xmit(struct libeth_xdp_tx_desc desc, u32 i,
> +				    const struct libeth_xdpsq *sq, u64 priv)
> +{
> +	struct idpf_flex_tx_desc *tx_desc = sq->descs;
> +	u32 cmd;
> +
> +	cmd = FIELD_PREP(IDPF_FLEX_TXD_QW1_DTYPE_M,
> +			 IDPF_TX_DESC_DTYPE_FLEX_L2TAG1_L2TAG2);
> +	if (desc.flags & LIBETH_XDP_TX_LAST)
> +		cmd |= FIELD_PREP(IDPF_FLEX_TXD_QW1_CMD_M,
> +				  IDPF_TX_DESC_CMD_EOP);
> +	if (priv && (desc.flags & LIBETH_XDP_TX_CSUM))
> +		cmd |= FIELD_PREP(IDPF_FLEX_TXD_QW1_CMD_M,
> +				  IDPF_TX_FLEX_DESC_CMD_CS_EN);
> +
> +	tx_desc = &tx_desc[i];
> +	tx_desc->buf_addr = cpu_to_le64(desc.addr);
> +#ifdef __LIBETH_WORD_ACCESS
> +	*(u64 *)&tx_desc->qw1 = ((u64)desc.len << 48) | cmd;
> +#else
> +	tx_desc->qw1.buf_size = cpu_to_le16(desc.len);
> +	tx_desc->qw1.cmd_dtype = cpu_to_le16(cmd);
> +#endif
> +}
> +
> +/**
> + * idpf_set_rs_bit - set RS bit on last produced descriptor
> + * @xdpq: XDP queue to produce the HW Tx descriptors on
> + */
> +static inline void idpf_set_rs_bit(const struct idpf_tx_queue *xdpq)
> +{
> +	u32 ntu, cmd;
> +
> +	ntu = xdpq->next_to_use;
> +	if (unlikely(!ntu))
> +		ntu = xdpq->desc_count;
> +
> +	cmd = FIELD_PREP(IDPF_FLEX_TXD_QW1_CMD_M, IDPF_TX_DESC_CMD_RS);
> +#ifdef __LIBETH_WORD_ACCESS
> +	*(u64 *)&xdpq->flex_tx[ntu - 1].q.qw1 |= cmd;
> +#else
> +	xdpq->flex_tx[ntu - 1].q.qw1.cmd_dtype |= cpu_to_le16(cmd);
> +#endif
> +}
> +
> +/**
> + * idpf_xdpq_update_tail - update the XDP Tx queue tail register
> + * @xdpq: XDP Tx queue
> + */
> +static inline void idpf_xdpq_update_tail(const struct idpf_tx_queue *xdpq)
> +{
> +	dma_wmb();
> +	writel_relaxed(xdpq->next_to_use, xdpq->tail);
> +}
> +
> +/**
> + * idpf_xdp_tx_finalize - Update RS bit and bump XDP Tx tail
> + * @_xdpq: XDP Tx queue
> + * @sent: whether any frames were sent
> + * @flush: whether to update RS bit and the tail register
> + *
> + * This function bumps XDP Tx tail and should be called when a batch of packets
> + * has been processed in the napi loop.
> + */
> +static inline void idpf_xdp_tx_finalize(void *_xdpq, bool sent, bool flush)
> +{
> +	struct idpf_tx_queue *xdpq = _xdpq;
> +
> +	if ((!flush || unlikely(!sent)) &&
> +	    likely(xdpq->desc_count != xdpq->pending))
> +		return;
> +
> +	libeth_xdpsq_lock(&xdpq->xdp_lock);
> +
> +	idpf_set_rs_bit(xdpq);
> +	idpf_xdpq_update_tail(xdpq);
> +
> +	libeth_xdpsq_queue_timer(xdpq->timer);
> +
> +	libeth_xdpsq_unlock(&xdpq->xdp_lock);
> +}
> +
> +void idpf_xdp_set_features(const struct idpf_vport *vport);
> +
>  int idpf_xdp(struct net_device *dev, struct netdev_bpf *xdp);
>  
>  #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 84ca8c08bd56..2d1efcb854be 100644
> --- a/drivers/net/ethernet/intel/idpf/idpf_lib.c
> +++ b/drivers/net/ethernet/intel/idpf/idpf_lib.c
> @@ -814,6 +814,8 @@ static int idpf_cfg_netdev(struct idpf_vport *vport)
>  	netdev->features |= dflt_features;
>  	netdev->hw_features |= dflt_features | offloads;
>  	netdev->hw_enc_features |= dflt_features | offloads;
> +	idpf_xdp_set_features(vport);
> +
>  	idpf_set_ethtool_ops(netdev);
>  	netif_set_affinity_auto(netdev);
>  	SET_NETDEV_DEV(netdev, &adapter->pdev->dev);
> diff --git a/drivers/net/ethernet/intel/idpf/idpf_txrx.c b/drivers/net/ethernet/intel/idpf/idpf_txrx.c
> index f25c50d8947b..cddcc5fc291f 100644
> --- a/drivers/net/ethernet/intel/idpf/idpf_txrx.c
> +++ b/drivers/net/ethernet/intel/idpf/idpf_txrx.c
> @@ -1,8 +1,6 @@
>  // SPDX-License-Identifier: GPL-2.0-only
>  /* Copyright (C) 2023 Intel Corporation */
>  
> -#include <net/libeth/xdp.h>
> -
>  #include "idpf.h"
>  #include "idpf_virtchnl.h"
>  #include "xdp.h"
> @@ -3247,14 +3245,12 @@ static bool idpf_rx_process_skb_fields(struct sk_buff *skb,
>  	return !__idpf_rx_process_skb_fields(rxq, skb, xdp->desc);
>  }
>  
> -static void
> -idpf_xdp_run_pass(struct libeth_xdp_buff *xdp, struct napi_struct *napi,
> -		  struct libeth_rq_napi_stats *ss,
> -		  const struct virtchnl2_rx_flex_desc_adv_nic_3 *desc)
> -{
> -	libeth_xdp_run_pass(xdp, NULL, napi, ss, desc, NULL,
> -			    idpf_rx_process_skb_fields);
> -}
> +LIBETH_XDP_DEFINE_START();
> +LIBETH_XDP_DEFINE_RUN(static idpf_xdp_run_pass, idpf_xdp_run_prog,
> +		      idpf_xdp_tx_flush_bulk, idpf_rx_process_skb_fields);
> +LIBETH_XDP_DEFINE_FINALIZE(static idpf_xdp_finalize_rx, idpf_xdp_tx_flush_bulk,
> +			   idpf_xdp_tx_finalize);
> +LIBETH_XDP_DEFINE_END();
>  
>  /**
>   * idpf_rx_hsplit_wa - handle header buffer overflows and split errors
> @@ -3338,9 +3334,12 @@ static int idpf_rx_splitq_clean(struct idpf_rx_queue *rxq, int budget)
>  {
>  	struct idpf_buf_queue *rx_bufq = NULL;
>  	struct libeth_rq_napi_stats rs = { };
> +	struct libeth_xdp_tx_bulk bq;
>  	LIBETH_XDP_ONSTACK_BUFF(xdp);
>  	u16 ntc = rxq->next_to_clean;
>  
> +	libeth_xdp_tx_init_bulk(&bq, rxq->xdp_prog, rxq->xdp_rxq.dev,
> +				rxq->xdpqs, rxq->num_xdp_txq);
>  	libeth_xdp_init_buff(xdp, &rxq->xdp, &rxq->xdp_rxq);
>  
>  	/* Process Rx packets bounded by budget */
> @@ -3435,11 +3434,13 @@ static int idpf_rx_splitq_clean(struct idpf_rx_queue *rxq, int budget)
>  		if (!idpf_rx_splitq_is_eop(rx_desc) || unlikely(!xdp->data))
>  			continue;
>  
> -		idpf_xdp_run_pass(xdp, rxq->napi, &rs, rx_desc);
> +		idpf_xdp_run_pass(xdp, &bq, rxq->napi, &rs, rx_desc);
>  	}
>  
>  	rxq->next_to_clean = ntc;
> +
>  	libeth_xdp_save_buff(&rxq->xdp, xdp);
> +	idpf_xdp_finalize_rx(&bq);
>  
>  	u64_stats_update_begin(&rxq->stats_sync);
>  	u64_stats_add(&rxq->q_stats.packets, rs.packets);
> diff --git a/drivers/net/ethernet/intel/idpf/xdp.c b/drivers/net/ethernet/intel/idpf/xdp.c
> index c0322fa7bfee..abf75e840c0a 100644
> --- a/drivers/net/ethernet/intel/idpf/xdp.c
> +++ b/drivers/net/ethernet/intel/idpf/xdp.c
> @@ -1,8 +1,6 @@
>  // SPDX-License-Identifier: GPL-2.0-only
>  /* Copyright (C) 2024 Intel Corporation */
>  
> -#include <net/libeth/xdp.h>
> -
>  #include "idpf.h"
>  #include "idpf_virtchnl.h"
>  #include "xdp.h"
> @@ -143,6 +141,8 @@ void idpf_copy_xdp_prog_to_qs(const struct idpf_vport *vport,
>  	idpf_rxq_for_each(vport, idpf_xdp_rxq_assign_prog, xdp_prog);
>  }
>  
> +static void idpf_xdp_tx_timer(struct work_struct *work);
> +
>  int idpf_vport_xdpq_get(const struct idpf_vport *vport)
>  {
>  	struct libeth_xdpsq_timer **timers __free(kvfree) = NULL;
> @@ -183,6 +183,8 @@ int idpf_vport_xdpq_get(const struct idpf_vport *vport)
>  
>  		xdpq->timer = timers[i - sqs];
>  		libeth_xdpsq_get(&xdpq->xdp_lock, dev, vport->xdpq_share);
> +		libeth_xdpsq_init_timer(xdpq->timer, xdpq, &xdpq->xdp_lock,
> +					idpf_xdp_tx_timer);
>  
>  		xdpq->pending = 0;
>  		xdpq->xdp_tx = 0;
> @@ -209,6 +211,7 @@ void idpf_vport_xdpq_put(const struct idpf_vport *vport)
>  		if (!idpf_queue_has_clear(XDP, xdpq))
>  			continue;
>  
> +		libeth_xdpsq_deinit_timer(xdpq->timer);
>  		libeth_xdpsq_put(&xdpq->xdp_lock, dev);
>  
>  		kfree(xdpq->timer);
> @@ -216,6 +219,154 @@ void idpf_vport_xdpq_put(const struct idpf_vport *vport)
>  	}
>  }
>  
> +static int
> +idpf_xdp_parse_compl_desc(const struct idpf_splitq_4b_tx_compl_desc *desc,
> +			  bool gen)
> +{
> +	u32 val;
> +
> +#ifdef __LIBETH_WORD_ACCESS
> +	val = *(const u32 *)desc;
> +#else
> +	val = ((u32)le16_to_cpu(desc->q_head_compl_tag.q_head) << 16) |
> +	      le16_to_cpu(desc->qid_comptype_gen);
> +#endif
> +	if (!!(val & IDPF_TXD_COMPLQ_GEN_M) != gen)
> +		return -ENODATA;
> +
> +	if (unlikely((val & GENMASK(IDPF_TXD_COMPLQ_GEN_S - 1, 0)) !=
> +		     FIELD_PREP(IDPF_TXD_COMPLQ_COMPL_TYPE_M,
> +				IDPF_TXD_COMPLT_RS)))
> +		return -EINVAL;
> +
> +	return upper_16_bits(val);
> +}
> +
> +static u32 idpf_xdpsq_poll(struct idpf_tx_queue *xdpsq, u32 budget)
> +{
> +	struct idpf_compl_queue *cq = xdpsq->complq;
> +	u32 tx_ntc = xdpsq->next_to_clean;
> +	u32 tx_cnt = xdpsq->desc_count;
> +	u32 ntc = cq->next_to_clean;
> +	u32 cnt = cq->desc_count;
> +	u32 done_frames;
> +	bool gen;
> +
> +	gen = idpf_queue_has(GEN_CHK, cq);
> +
> +	for (done_frames = 0; done_frames < budget; ) {
> +		int ret;
> +
> +		ret = idpf_xdp_parse_compl_desc(&cq->comp_4b[ntc], gen);
> +		if (ret >= 0) {
> +			done_frames = ret > tx_ntc ? ret - tx_ntc :
> +						     ret + tx_cnt - tx_ntc;
> +			goto next;
> +		}
> +
> +		switch (ret) {
> +		case -ENODATA:
> +			goto out;
> +		case -EINVAL:
> +			break;
> +		}
> +
> +next:
> +		if (unlikely(++ntc == cnt)) {
> +			ntc = 0;
> +			gen = !gen;
> +			idpf_queue_change(GEN_CHK, cq);
> +		}
> +	}
> +
> +out:
> +	cq->next_to_clean = ntc;
> +
> +	return done_frames;
> +}
> +
> +/**
> + * idpf_clean_xdp_irq - Reclaim a batch of TX resources from completed XDP_TX
> + * @_xdpq: XDP Tx queue
> + * @budget: maximum number of descriptors to clean
> + *
> + * Returns number of cleaned descriptors.
> + */
> +static u32 idpf_clean_xdp_irq(void *_xdpq, u32 budget)
> +{
> +	struct libeth_xdpsq_napi_stats ss = { };
> +	struct idpf_tx_queue *xdpq = _xdpq;
> +	u32 tx_ntc = xdpq->next_to_clean;
> +	u32 tx_cnt = xdpq->desc_count;
> +	struct xdp_frame_bulk bq;
> +	struct libeth_cq_pp cp = {
> +		.dev	= xdpq->dev,
> +		.bq	= &bq,
> +		.xss	= &ss,
> +		.napi	= true,
> +	};
> +	u32 done_frames;
> +
> +	done_frames = idpf_xdpsq_poll(xdpq, budget);

nit: maybe pass {tx_ntc, tx_cnt} to the above?

> +	if (unlikely(!done_frames))
> +		return 0;
> +
> +	xdp_frame_bulk_init(&bq);
> +
> +	for (u32 i = 0; likely(i < done_frames); i++) {
> +		libeth_xdp_complete_tx(&xdpq->tx_buf[tx_ntc], &cp);
> +
> +		if (unlikely(++tx_ntc == tx_cnt))
> +			tx_ntc = 0;
> +	}
> +
> +	xdp_flush_frame_bulk(&bq);
> +
> +	xdpq->next_to_clean = tx_ntc;
> +	xdpq->pending -= done_frames;
> +	xdpq->xdp_tx -= cp.xdp_tx;

not following this variable. __libeth_xdp_complete_tx() decresases
libeth_cq_pp::xdp_tx by libeth_sqe::nr_frags. can you shed more light
what's going on here?

> +
> +	return done_frames;
> +}
> +
> +static u32 idpf_xdp_tx_prep(void *_xdpq, struct libeth_xdpsq *sq)
> +{
> +	struct idpf_tx_queue *xdpq = _xdpq;
> +	u32 free;
> +
> +	libeth_xdpsq_lock(&xdpq->xdp_lock);
> +
> +	free = xdpq->desc_count - xdpq->pending;
> +	if (free <= xdpq->thresh)
> +		free += idpf_clean_xdp_irq(xdpq, xdpq->thresh);
> +
> +	*sq = (struct libeth_xdpsq){

could you have libeth_xdpsq embedded in idpf_tx_queue and avoid that
initialization?

> +		.sqes		= xdpq->tx_buf,
> +		.descs		= xdpq->desc_ring,
> +		.count		= xdpq->desc_count,
> +		.lock		= &xdpq->xdp_lock,
> +		.ntu		= &xdpq->next_to_use,
> +		.pending	= &xdpq->pending,
> +		.xdp_tx		= &xdpq->xdp_tx,
> +	};
> +
> +	return free;
> +}
> +
> +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_END();
> +
> +void idpf_xdp_set_features(const struct idpf_vport *vport)
> +{
> +	if (!idpf_is_queue_model_split(vport->rxq_model))
> +		return;
> +
> +	libeth_xdp_set_features_noredir(vport->netdev);
> +}
> +
>  /**
>   * idpf_xdp_setup_prog - handle XDP program install/remove requests
>   * @vport: vport to configure
> -- 
> 2.48.1
> 

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