linux-kernel - Re: [PATCH 1/2] iommu/mediatek-v1: Alloc building as module

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Date:   Thu, 25 Mar 2021 17:42:09 +0000
From:   Robin Murphy <robin.murphy@....com>
To:     Will Deacon <will@...nel.org>, Yong Wu <yong.wu@...iatek.com>
Cc:     Joerg Roedel <joro@...tes.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Tomasz Figa <tfiga@...omium.com>,
        linux-mediatek@...ts.infradead.org, srv_heupstream@...iatek.com,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        iommu@...ts.linux-foundation.org,
        Krzysztof Kozlowski <krzk@...nel.org>, youlin.pei@...iatek.com,
        Nicolas Boichat <drinkcat@...omium.org>, anan.sun@...iatek.com,
        chao.hao@...iatek.com
Subject: Re: [PATCH 1/2] iommu/mediatek-v1: Alloc building as module

^^Nit: presumably you meant "Allow" in the subject.

On 2021-03-25 17:16, Will Deacon wrote:
> On Tue, Mar 23, 2021 at 01:58:00PM +0800, Yong Wu wrote:
>> This patch only adds support for building the IOMMU-v1 driver as module.
>> Correspondingly switch the config to tristate.
>>
>> Signed-off-by: Yong Wu <yong.wu@...iatek.com>
>> ---
>> rebase on v5.12-rc2.
>> ---
>>   drivers/iommu/Kconfig        | 2 +-
>>   drivers/iommu/mtk_iommu_v1.c | 9 ++++-----
>>   2 files changed, 5 insertions(+), 6 deletions(-)
> 
> Both of these patches look fine to me, but you probably need to check
> the setting of MODULE_OWNER after:
> 
> https://lore.kernel.org/r/f4de29d8330981301c1935e667b507254a2691ae.1616157612.git.robin.murphy@arm.com

Right, furthermore I would rather expect these patches on their own to 
hit the problem that my patch tries to avoid - where since mtk_iommu_ops 
is const, the current version of iommu_device_set_ops() is liable to 
blow up trying to write to rodata.

In fact I do wonder a little why that wasn't happening already - maybe 
the compiler is clever enough to tell that the assignment is redundant 
when THIS_MODULE == 0, and elides it :/

Robin.