linux-kernel - Re: [PATCH 2/2] ARC: mm: fix new code about cache aliasing

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Message-ID: <abb3f8ab-c88d-4b04-ae75-62de0dddd343@kernel.org>
Date: Thu, 28 Mar 2024 10:22:52 -0700
From: Vineet Gupta <vgupta@...nel.org>
To: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
 Vineet Gupta <vgupta@...nel.org>, linux-snps-arc@...ts.infradead.org,
 Andrew Morton <akpm@...ux-foundation.org>
Cc: linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org
Subject: Re: [PATCH 2/2] ARC: mm: fix new code about cache aliasing



On 3/28/24 06:57, Mathieu Desnoyers wrote:
> On 2024-03-28 01:39, Vineet Gupta wrote:
>> Manual/partial revert of 8690bbcf3b70 ("Introduce cpu_dcache_is_aliasing() across all architectures")
>>
>> Current generation of ARCv2/ARCv3 based HSxx cores are only PIPT (to software
>> at least).
>>
>> Legacy ARC700 cpus could be VIPT aliasing (based on cache geometry and
>> PAGE_SIZE) however recently that support was ripped out so VIPT aliasing
>> cache is not relevant to ARC anymore.
>>
>> P.S. : This has been discussed a few times on lists [1]
>> P.S.2: Please CC the arch maintainers and/or mailing list before adding
>>         such interfaces.
> Because 8690bbcf3b70 was introducing a tree-wide change affecting all
> architectures, I CC'd linux-arch@...r.kernel.org. I expected all
> architecture maintainers to follow that list, which is relatively
> low volume.

Ideally yeah arch maintainers should be lurking there.


> I'm sorry that you learn about this after the fact as a result.

Please don't be, no harm done, the fix was easy ;-)

> My intent was to use the list rather than CC about 50 additional
> people/mailing lists.

That is true but I don't think maintainers mind that in general. I still
posit that any new interfaces to arch code should be explicitly run by them.

> Of course, if VIPT aliasing is removed from ARC, removing the
> config ARCH_HAS_CPU_CACHE_ALIASING and using the generic
> cpu_dcache_is_aliasing() is the way to go. Feel free to add
> my:
>
> Acked-by: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>

Thx,
-Vineet