linux-kernel - Re: [PATCH net v3 1/1] i40e: xsk: advance next_to

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Message-ID: <aRtPXS8haLNHu8H1@boxer>
Date: Mon, 17 Nov 2025 17:37:49 +0100
From: Maciej Fijalkowski <maciej.fijalkowski@...el.com>
To: Alessandro Decina <alessandro.d@...il.com>
CC: <netdev@...r.kernel.org>, "David S. Miller" <davem@...emloft.net>, "Alexei
 Starovoitov" <ast@...nel.org>, Andrew Lunn <andrew+netdev@...n.ch>, "Daniel
 Borkmann" <daniel@...earbox.net>, Eric Dumazet <edumazet@...gle.com>, "Jakub
 Kicinski" <kuba@...nel.org>, Jesper Dangaard Brouer <hawk@...nel.org>, "John
 Fastabend" <john.fastabend@...il.com>, Paolo Abeni <pabeni@...hat.com>,
	Przemek Kitszel <przemyslaw.kitszel@...el.com>, Stanislav Fomichev
	<sdf@...ichev.me>, Tirthendu Sarkar <tirthendu.sarkar@...el.com>, Tony Nguyen
	<anthony.l.nguyen@...el.com>, <bpf@...r.kernel.org>,
	<intel-wired-lan@...ts.osuosl.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH net v3 1/1] i40e: xsk: advance next_to_clean on status
 descriptors

On Sat, Nov 15, 2025 at 06:58:41PM +1100, Alessandro Decina wrote:
> On Fri, Nov 14, 2025 at 02:01:14PM +0100, Maciej Fijalkowski wrote:
> > Woah, that's not what I had on mind...I meant to pull whole block that
> > takes care of FDIR descriptors onto common function. That logic should be
> > shared between normal Rx and ZC Rx. The only different action we need to
> > take is how we release the buffer.
> > 
> > Could you try pulling whole i40e_rx_is_programming_status() branch onto
> > function within i40e_txrx_common.h and see how much of a work would it
> > take to have this as a common function?
> 
> Just before I send another rev, you mean something like this? 
> https://github.com/alessandrod/linux/commit/a6fa91d5b5d1cc283a2f1faa378085c44bda8b4a
> 
> My rationale for i40e_inc_ntp_ntc was that _that_ is where the bug lies:
> letting ntp and ntc get out of sync. By introducing a function that
> forces you to _have_ to think about ntc and explicitly pass NULL if you
> don't want to sync it, bugs like this become less easy to introduce.
> 
> That said I don't mind either way! Let me know if you want me to send v4
> with the i40e_clean_programming_status() change.

This revision is much more clear to me. Only thing that might be bothering
someone is doubled i40e_rx_bi() call in i40e_get_rx_buffer(). Not sure if
we can do about it though as we need to use ntp from before potential
increment.

...maybe pass rx_buffer to i40e_get_rx_buffer() ?

> 
> Ciao,
> Alessandro