linux-kernel - Re: [PATCH] drm/imagination: Align rogue_fwif

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Message-ID: <a03d7321-4394-494f-86fb-b0394d5c4148@imgtec.com>
Date: Mon, 5 Jan 2026 13:52:27 +0000
From: Matt Coster <Matt.Coster@...tec.com>
To: Michal Wilczynski <m.wilczynski@...sung.com>
CC: Frank Binns <Frank.Binns@...tec.com>,
        Alessio Belle
	<Alessio.Belle@...tec.com>,
        Alexandru Dadu <Alexandru.Dadu@...tec.com>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard
	<mripard@...nel.org>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        David Airlie
	<airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
        kernel test robot
	<lkp@...el.com>,
        "dri-devel@...ts.freedesktop.org"
	<dri-devel@...ts.freedesktop.org>,
        "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] drm/imagination: Align rogue_fwif_hwrtdata to 64 bytes

On 22/12/2025 22:53, Michal Wilczynski wrote:
> The build fails on RISC-V using GCC because `SIZE_CHECK(struct
> rogue_fwif_hwrtdata, 384)` expects 384 bytes, but the compiler generates
> a 336-byte structure.
> 
> This is due to an alignment conflict: the inner member `cleanup_state`
> requires 64-byte alignment, but the outer struct is explicitly marked
> `__aligned(8)`.
> 
> While GCC on ARM64 implicitly pads the size to a multiple of 64, GCC on
> RISC-V strictly respects the 8-byte outer alignment, resulting in a size
> mismatch.
> 
> Fix this by aligning the entire structure to 64 bytes, which resolves
> the contradiction and forces the correct 384 byte size on all
> architectures.
> 
> Fixes: a26f067feac1 ("drm/imagination: Add FWIF headers")
> Reported-by: kernel test robot <lkp@...el.com>
> Closes: https://lore.kernel.org/oe-kbuild-all/202512131851.1WNXk3BC-lkp@intel.com/ 
> Signed-off-by: Michal Wilczynski <m.wilczynski@...sung.com>

Hi Michal,

This looks fine to me. I'm surprised the behaviour of GCC differs by
architecture though, is there a bug somewhere or is it UB to explicitly
narrow the alignment like this? Either way:

Reviewed-by: Matt Coster <matt.coster@...tec.com>

And I'll take via drm-misc-fixes tomorrow.

Cheers,
Matt

> ---
>  drivers/gpu/drm/imagination/pvr_rogue_fwif.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/imagination/pvr_rogue_fwif.h b/drivers/gpu/drm/imagination/pvr_rogue_fwif.h
> index 172886be4c820a32ae1b08d62bf0814250f2a9bd..1ba2a167a38b31911e0846923e4dc70626f5ca65 100644
> --- a/drivers/gpu/drm/imagination/pvr_rogue_fwif.h
> +++ b/drivers/gpu/drm/imagination/pvr_rogue_fwif.h
> @@ -2170,7 +2170,7 @@ struct rogue_fwif_hwrtdata {
>  	bool geom_caches_need_zeroing __aligned(4);
>  
>  	struct rogue_fwif_cleanup_ctl cleanup_state __aligned(64);
> -} __aligned(8);
> +} __aligned(64);
>  
>  /*
>   ******************************************************************************
> 
> ---
> base-commit: 8f0b4cce4481fb22653697cced8d0d04027cb1e8
> change-id: 20251222-fix_imagination-8ef0c94122c4
> 
> Best regards,

-- 
Matt Coster
E: matt.coster@...tec.com


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