linux-kernel - Re: [PATCH v3 1/4] cacheinfo: Check sib_leaf in cache_leaves_are

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Message-ID: <20230413-willing-ignition-176ca292846d@wendy>
Date:   Thu, 13 Apr 2023 11:04:25 +0100
From:   Conor Dooley <conor.dooley@...rochip.com>
To:     Pierre Gondois <pierre.gondois@....com>
CC:     <linux-kernel@...r.kernel.org>, Radu Rendec <rrendec@...hat.com>,
        Alexandre Ghiti <alexghiti@...osinc.com>,
        Will Deacon <will@...nel.org>,
        Sudeep Holla <sudeep.holla@....com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Palmer Dabbelt <palmer@...osinc.com>,
        Gavin Shan <gshan@...hat.com>
Subject: Re: [PATCH v3 1/4] cacheinfo: Check sib_leaf in
 cache_leaves_are_shared()

On Thu, Apr 13, 2023 at 11:14:31AM +0200, Pierre Gondois wrote:
> If there is no ACPI/DT information, it is assumed that L1 caches
> are private and L2 (and higher) caches are shared. A cache is
> 'shared' between two CPUs if it is accessible from these two
> CPUs.
> 
> Each CPU owns a representation (i.e. has a dedicated cacheinfo struct)
> of the caches it has access to. cache_leaves_are_shared() tries to
> identify whether two representations are designating the same actual
> cache.
> 
> In cache_leaves_are_shared(), if 'this_leaf' is a L2 cache (or higher)
> and 'sib_leaf' is a L1 cache, the caches are detected as shared as
> only this_leaf's cache level is checked.
> This is leads to setting sib_leaf as being shared with another CPU,
> which is incorrect as this is a L1 cache.
> 
> Check 'sib_leaf->level'. Also update the comment as the function is
> called when populating 'shared_cpu_map'.
> 
> Fixes: f16d1becf96f ("cacheinfo: Use cache identifiers to check if the caches are shared if available")

Cool, thanks for the updated commit message. Easier to twig the
rationale this way.
Reviewed-by: Conor Dooley <conor.dooley@...rochip.com>

Thanks,
Conor.

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