netdev - Re: [PATCH 2/2 bpf v2] xsk: avoid data corruption on cq descriptor number

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Message-ID: <20251028160107.5c161a4f@kernel.org>
Date: Tue, 28 Oct 2025 16:01:07 -0700
From: Jakub Kicinski <kuba@...nel.org>
To: Fernando Fernandez Mancera <fmancera@...e.de>
Cc: bpf@...r.kernel.org, netdev@...r.kernel.org, magnus.karlsson@...el.com,
 maciej.fijalkowski@...el.com, sdf@...ichev.me, kerneljasonxing@...il.com,
 fw@...len.de
Subject: Re: [PATCH 2/2 bpf v2] xsk: avoid data corruption on cq descriptor
 number

On Tue, 28 Oct 2025 19:30:32 +0100 Fernando Fernandez Mancera wrote:
> Since commit 30f241fcf52a ("xsk: Fix immature cq descriptor
> production"), the descriptor number is stored in skb control block and
> xsk_cq_submit_addr_locked() relies on it to put the umem addrs onto
> pool's completion queue.

Looking at the past discussion it sounds like you want to optimize 
the single descriptor case? Can you not use a magic pointer for that?

	#define XSK_DESTRUCT_SINGLE_BUF	(void *)1
	destructor_arg = XSK_DESTRUCT_SINGLE_BUF

Let's target this fix at net, please, I think the complexity here is
all in skbs paths.