linux-kernel - Re: [PATCH v2 1/3] cacheinfo: Check sib_leaf in cache_leaves_are

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Message-ID: <20230412-catalyze-putt-4a0d48042e4f@spud>
Date:   Wed, 12 Apr 2023 14:50:01 +0100
From:   Conor Dooley <conor@...nel.org>
To:     Pierre Gondois <pierre.gondois@....com>
Cc:     Conor Dooley <conor.dooley@...rochip.com>,
        linux-kernel@...r.kernel.org, Radu Rendec <rrendec@...hat.com>,
        Alexandre Ghiti <alexghiti@...osinc.com>,
        Will Deacon <will@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Sudeep Holla <sudeep.holla@....com>,
        Palmer Dabbelt <palmer@...osinc.com>,
        Gavin Shan <gshan@...hat.com>,
        Jeremy Linton <jeremy.linton@....com>
Subject: Re: [PATCH v2 1/3] cacheinfo: Check sib_leaf in
 cache_leaves_are_shared()

On Wed, Apr 12, 2023 at 03:20:19PM +0200, Pierre Gondois wrote:
> > On Wed, Apr 12, 2023 at 02:34:11PM +0200, Pierre Gondois wrote:

> > Another silly question:
> > For two caches of level M & N; M != N; M, N > 1 should they be detected
> > as shared in the absence of any information in DT/ACPI?
> > The comment (to me) reads as if they should not, but it is rather vague.
> 
> I think they should. The naming of cache_leaves_are_shared() might be
> misleading. The function is more trying to find out if 2 cache leaves struct
> are representing the same cache. So maybe renaming the function to
> cache_leaves_identical() might be better?

Nah, I don't think this is really the fault of anything other than the
!DT && !ACPI situation.
I'm just trying to make sure I understand the intended behaviour in that
scenario, that's all.

> If there is no DT/ACPI, it is not possible to identify whether 2 cache leaves
> are representing the same cache. The desired behaviour is just:
> - If this_leaf or sib_leaf is a L1 cache, then the caches are not identical
>   (or shared if we use this wording)

> So the meaning of cache_leaves_identical() is a bit bent for this
> configuration.

Fair enough.

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