linux-kernel - Re: [linux-next20250912] Build warnings at drivers/net/ethernet/intel/idpf/xdp.c:6

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Message-Id: <3BDEECFD-5267-4453-B45B-07D3A1545D75@linux.ibm.com>
Date: Mon, 13 Oct 2025 09:27:14 +0530
From: Venkat <venkat88@...ux.ibm.com>
To: Alexander Lobakin <aleksander.lobakin@...el.com>,
        Madhavan Srinivasan <maddy@...ux.ibm.com>
Cc: Stephen Rothwell <sfr@...b.auug.org.au>,
        Madhavan Srinivasan <maddy@...ux.ibm.com>, michal.kubiak@...el.com,
        ramu.r@...el.com, anthony.l.nguyen@...el.com,
        LKML <linux-kernel@...r.kernel.org>,
        linuxppc-dev <linuxppc-dev@...ts.ozlabs.org>,
        Linux Next Mailing List <linux-next@...r.kernel.org>
Subject: Re: [linux-next20250912] Build warnings at
 drivers/net/ethernet/intel/idpf/xdp.c:6



> On 12 Sep 2025, at 7:00 PM, Alexander Lobakin <aleksander.lobakin@...el.com> wrote:
> 
> From: Venkat Rao Bagalkote <venkat88@...ux.ibm.com>
> Date: Fri, 12 Sep 2025 18:39:33 +0530
> 
>> Greetings!!!
>> 
>> 
>> IBM CI has reported a build warning on IBM Power Server, on linux-
>> next20250912 kernel.
>> 
>> 
>> gcc version 11.5.0 20240719 (Red Hat 11.5.0-2) (GCC)
>> 
>> GNU ld version 2.35.2-54.el9
>> 
>> 
>> Attached is the .config file.
>> 
>> 
>> Warnings:
>> 
>> In file included from drivers/net/ethernet/intel/idpf/xdp.c:6:
>> drivers/net/ethernet/intel/idpf/xdp.h: In function ‘idpf_xdp_tx_xmit’:
>> drivers/net/ethernet/intel/idpf/xdp.h:28:20: note: the ABI of passing
>> aggregates with 16-byte alignment has changed in GCC 5
>>   28 | static inline void idpf_xdp_tx_xmit(struct libeth_xdp_tx_desc
>> desc, u32 i,
>>      |                    ^~~~~~~~~~~~~~~~
> 
> Yes, I do pass 16-byte variables/structures directly.
> 
> I would say this warning makes no sense, due to the following reasons:
> 
> 1. IIRC the minimum required GCC version for building the latest kernel
>   is way above 5.
> 2. This warning should appear only with `-Wabi`, which the upstream
>   kernel never sets.

Now, this warning is seen on upstream kernel also. 

Not sure if this is something we need to fix it or suppress the warning?

Regards,
Venkat.

> 3. Kernel is a self-contained project, this function is not uAPI, so we
>   shouldn't care in general about backward ABI compatibility for purely
>   in-kernel stuff.
> 
> We have plenty of functions, mostly generic, which either passes or
> returns >= 16-byte objects, but I see this warning for the first time.
> Despite that my repo is attached to the open Intel CI bots infra which
> does daily builds on a good bunch of different architectures and
> toolchains (inc. GCC 8+).
> 
>> 
>> 
>> Git bisect is pointing below commit as the first bad commit.
>> 
>> 
>> first bad commit: [cba102cd719029a10bda1d0ca00ed646796f1f21] idpf: add
>> support for XDP on Rx
> 
> Thanks,
> Olek