linux-kernel - Re: [PATCH 04/33] ACPI / PPTT: Find cache level by cache-id

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Message-ID: <b87ef0cb-5859-4cd1-a0b0-3f0444484ffc@redhat.com>
Date: Sat, 8 Nov 2025 15:11:33 +1000
From: Gavin Shan <gshan@...hat.com>
To: Ben Horgan <ben.horgan@....com>, james.morse@....com
Cc: amitsinght@...vell.com, baisheng.gao@...soc.com,
 baolin.wang@...ux.alibaba.com, bobo.shaobowang@...wei.com,
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 jeremy.linton@....com, jonathan.cameron@...wei.com, kobak@...dia.com,
 lcherian@...vell.com, lenb@...nel.org, linux-acpi@...r.kernel.org,
 linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
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Subject: Re: [PATCH 04/33] ACPI / PPTT: Find cache level by cache-id

On 11/7/25 10:34 PM, Ben Horgan wrote:
> From: James Morse <james.morse@....com>
> 
> The MPAM table identifies caches by id. The MPAM driver also wants to know
> the cache level to determine if the platform is of the shape that can be
> managed via resctrl. Cacheinfo has this information, but only for CPUs that
> are online.
> 
> Waiting for all CPUs to come online is a problem for platforms where
> CPUs are brought online late by user-space.
> 
> Add a helper that walks every possible cache, until it finds the one
> identified by cache-id, then return the level.
> 
> Signed-off-by: James Morse <james.morse@....com>
> Signed-off-by: Ben Horgan <ben.horgan@....com>
> ---
> Changes since v3:
> Tags dropped due to rework
> Fallout/simplification from adding acpi_pptt_cache_v1_full
> Look for each cache type before incrementing level
> ---
>   drivers/acpi/pptt.c  | 63 ++++++++++++++++++++++++++++++++++++++++++++
>   include/linux/acpi.h |  5 ++++
>   2 files changed, 68 insertions(+)
> 

Reviewed-by: Gavin Shan <gshan@...hat.com>