linux-kernel - Re: [PATCH] drm/amd/amdgpu: Properly tune the size of struct

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Message-ID: <c12c4031-52fb-25a2-b411-e668eb9baaa2@tom.com>
Date:   Tue, 20 Jun 2023 15:57:22 +0800
From:   Longsuhui <Jack_sun@....com>
To:     Dan Carpenter <dan.carpenter@...aro.org>,
        Su Hui <suhui@...china.com>
Cc:     alexander.deucher@....com, airlied@...il.com, Xinhui.Pan@....com,
        daniel@...ll.ch, David.Francis@....com, Jane.Jian@....com,
        Bokun.Zhang@....com, monk.liu@....com,
        amd-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org
Subject: Re: [PATCH] drm/amd/amdgpu: Properly tune the size of struct

On 2023/6/20 15:37, Dan Carpenter wrote:
> On Tue, Jun 20, 2023 at 12:59:19PM +0800, Su Hui wrote:
>> Smatch error:
>>      gpu/drm/amd/amdgpu/amdgv_sriovmsg.h:316:49: error:
>>      static assertion failed: "amd_sriov_msg_pf2vf_info must be 1 KB"
>>      static assertion failed: "amd_sriov_msg_vf2pf_info must be 1 KB"
>>
> I doubt that moving the struct members around is safe.  This looks like
> it's in a very specific order.  So I don't think this patch is correct.
>
> The reason for this false positive this code uses a #pragma to pack the
> struct.
>
> #pragma pack(push, 1) // PF2VF / VF2PF data areas are byte packed

Oh, Sorry, I didn't see this code.

This patch is error, and sorry for the noise.

> Sparse does not support this and Smatch uses Sparse as a parser.  The
> main reason why Sparse doesn't support this pragma is because Linus
> thinks it's gross.  You probably didn't even see the #pragma did you?
> And anything you can't see is unreadable by definition.
>
> "Mark the associated types properly packed individually, rather than
> use the disgusting "pragma pack()" that should never be used."
>
> https://lore.kernel.org/linux-sparse/CAHk-=wi7jGZ+bVbt-UfXOkpEQdHzF3Z2HBjkGdjh8q4dvPPGWQ@mail.gmail.com/
>
> regards,
> dan carpenter