linux-kernel - Re: [Intel-wired-lan] [PATCH] [v2] ethernet: intel: fix building with large NR

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Message-ID: <dc2d8a33-644f-4f45-af59-04531e40a79a@intel.com>
Date: Tue, 24 Jun 2025 16:10:04 +0200
From: Alexander Lobakin <aleksander.lobakin@...el.com>
To: Arnd Bergmann <arnd@...nel.org>
CC: 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>, Arnd Bergmann
	<arnd@...db.de>, Simon Horman <horms@...nel.org>, "Dr. David Alan Gilbert"
	<linux@...blig.org>, Aleksandr Loktionov <aleksandr.loktionov@...el.com>,
	Dawid Osuchowski <dawid.osuchowski@...ux.intel.com>, Jedrzej Jagielski
	<jedrzej.jagielski@...el.com>, Mateusz Polchlopek
	<mateusz.polchlopek@...el.com>, Piotr Kwapulinski
	<piotr.kwapulinski@...el.com>, Slawomir Mrozowicz
	<slawomirx.mrozowicz@...el.com>, Martyna Szapar-Mudlaw
	<martyna.szapar-mudlaw@...ux.intel.com>, <intel-wired-lan@...ts.osuosl.org>,
	<netdev@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [Intel-wired-lan] [PATCH] [v2] ethernet: intel: fix building with
 large NR_CPUS

From: Arnd Bergmann <arnd@...nel.org>
Date: Fri, 20 Jun 2025 19:31:24 +0200

> From: Arnd Bergmann <arnd@...db.de>
> 
> With large values of CONFIG_NR_CPUS, three Intel ethernet drivers fail to
> compile like:
> 
> In function ‘i40e_free_q_vector’,
>     inlined from ‘i40e_vsi_alloc_q_vectors’ at drivers/net/ethernet/intel/i40e/i40e_main.c:12112:3:
>   571 |         _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
> include/linux/rcupdate.h:1084:17: note: in expansion of macro ‘BUILD_BUG_ON’
>  1084 |                 BUILD_BUG_ON(offsetof(typeof(*(ptr)), rhf) >= 4096);    \
> drivers/net/ethernet/intel/i40e/i40e_main.c:5113:9: note: in expansion of macro ‘kfree_rcu’
>  5113 |         kfree_rcu(q_vector, rcu);
>       |         ^~~~~~~~~
> 
> The problem is that the 'rcu' member in 'q_vector' is too far from the start
> of the structure. Move this member before the CPU mask instead, in all three
> drivers.
> 
> Signed-off-by: Arnd Bergmann <arnd@...db.de>

Reviewed-by: Alexander Lobakin <aleksander.lobakin@...el.com>

> ---
> v2: move rcu to just after the napi_struct [Alexander Lobakin]

Thanks!
Olek