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

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Date:   Mon, 27 Mar 2023 15:04:15 +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>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Sudeep Holla <sudeep.holla@....com>,
        Oliver Upton <oliver.upton@...ux.dev>,
        Akihiko Odaki <akihiko.odaki@...nix.com>,
        Palmer Dabbelt <palmer@...osinc.com>,
        Gavin Shan <gshan@...hat.com>,
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH 1/3] cacheinfo: Check sib_leaf in
 cache_leaves_are_shared()

On Mon, Mar 27, 2023 at 01:59:49PM +0200, Pierre Gondois wrote:
> If 'this_leaf' is a L2 cache (or higher) and 'sib_leaf' is a L1 cache,
> the caches are detected as shared.
> Indeed, cache_leaves_are_shared() only checks the cache level of
> 'this_leaf' when 'sib_leaf''s cache level should also be checked.

nit: this commit message reads quite weirdly as there's a missing "do
foo" statement, followed by "also do bar".

> 
> Also update the comment: the function is called when populating
> 'shared_cpu_map'.
> 
> Signed-off-by: Pierre Gondois <pierre.gondois@....com>
> ---
>  drivers/base/cacheinfo.c | 5 ++---
>  1 file changed, 2 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/base/cacheinfo.c b/drivers/base/cacheinfo.c
> index f6573c335f4c..4ca117574af1 100644
> --- a/drivers/base/cacheinfo.c
> +++ b/drivers/base/cacheinfo.c
> @@ -38,11 +38,10 @@ static inline bool cache_leaves_are_shared(struct cacheinfo *this_leaf,
>  {
>  	/*
>  	 * For non DT/ACPI systems, assume unique level 1 caches,
> -	 * system-wide shared caches for all other levels. This will be used
> -	 * only if arch specific code has not populated shared_cpu_map
> +	 * system-wide shared caches for all other levels.
>  	 */
>  	if (!(IS_ENABLED(CONFIG_OF) || IS_ENABLED(CONFIG_ACPI)))
> -		return !(this_leaf->level == 1);
> +		return (this_leaf->level != 1) || (sib_leaf->level != 1);

So this is
Fixes: f16d1becf96f ("cacheinfo: Use cache identifiers to check if the caches are shared if available")
then?

Cheers,
Conor.

>  
>  	if ((sib_leaf->attributes & CACHE_ID) &&
>  	    (this_leaf->attributes & CACHE_ID))
> -- 
> 2.25.1
> 
> 

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