netdev - Re: [PATCH net-next v2 2/9] xsk: add descs parameter in xskq_cons_read_desc

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Message-ID: <aKzTPW4fQ11fqb+b@boxer>
Date: Mon, 25 Aug 2025 23:18:53 +0200
From: Maciej Fijalkowski <maciej.fijalkowski@...el.com>
To: Jason Xing <kerneljasonxing@...il.com>
CC: <davem@...emloft.net>, <edumazet@...gle.com>, <kuba@...nel.org>,
	<pabeni@...hat.com>, <bjorn@...nel.org>, <magnus.karlsson@...el.com>,
	<jonathan.lemon@...il.com>, <sdf@...ichev.me>, <ast@...nel.org>,
	<daniel@...earbox.net>, <hawk@...nel.org>, <john.fastabend@...il.com>,
	<horms@...nel.org>, <andrew+netdev@...n.ch>, <bpf@...r.kernel.org>,
	<netdev@...r.kernel.org>, Jason Xing <kernelxing@...cent.com>
Subject: Re: [PATCH net-next v2 2/9] xsk: add descs parameter in
 xskq_cons_read_desc_batch()

On Mon, Aug 25, 2025 at 09:53:35PM +0800, Jason Xing wrote:
> From: Jason Xing <kernelxing@...cent.com>
> 
> Add a new parameter to let generic xmit call this interface in the
> subsequent patches.
> 
> Prior to this patch, pool->tx_descs in xskq_cons_read_desc_batch() is
> only used to store a small number of descs in zerocopy mode. Later
> another similar cache named xs->desc_batch will be used in copy mode.
> So adjust the parameter for copy mode.

Explain why you couldn't reuse tx_descs as-is. Pool can not work both in
copy and zero-copy modes at the same time so I don't see the reason why
you couldn't reuse this for your needs?

> 
> Signed-off-by: Jason Xing <kernelxing@...cent.com>
> ---
>  net/xdp/xsk.c       | 2 +-
>  net/xdp/xsk_queue.h | 3 +--
>  2 files changed, 2 insertions(+), 3 deletions(-)
> 
> diff --git a/net/xdp/xsk.c b/net/xdp/xsk.c
> index e75a6e2bab83..173ad49379c3 100644
> --- a/net/xdp/xsk.c
> +++ b/net/xdp/xsk.c
> @@ -509,7 +509,7 @@ u32 xsk_tx_peek_release_desc_batch(struct xsk_buff_pool *pool, u32 nb_pkts)
>  	if (!nb_pkts)
>  		goto out;
>  
> -	nb_pkts = xskq_cons_read_desc_batch(xs->tx, pool, nb_pkts);
> +	nb_pkts = xskq_cons_read_desc_batch(xs->tx, pool, pool->tx_descs, nb_pkts);
>  	if (!nb_pkts) {
>  		xs->tx->queue_empty_descs++;
>  		goto out;
> diff --git a/net/xdp/xsk_queue.h b/net/xdp/xsk_queue.h
> index 46d87e961ad6..47741b4c285d 100644
> --- a/net/xdp/xsk_queue.h
> +++ b/net/xdp/xsk_queue.h
> @@ -235,10 +235,9 @@ static inline void parse_desc(struct xsk_queue *q, struct xsk_buff_pool *pool,
>  
>  static inline
>  u32 xskq_cons_read_desc_batch(struct xsk_queue *q, struct xsk_buff_pool *pool,
> -			      u32 max)
> +			      struct xdp_desc *descs, u32 max)
>  {
>  	u32 cached_cons = q->cached_cons, nb_entries = 0;
> -	struct xdp_desc *descs = pool->tx_descs;
>  	u32 total_descs = 0, nr_frags = 0;
>  
>  	/* track first entry, if stumble upon *any* invalid descriptor, rewind
> -- 
> 2.41.3
>