linux-kernel - Re: [PATCH 11/33] arm_mpam: Add the class and component structures for firmware described ris

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Message-ID: <4d68d1b7-e3c9-4692-aba8-4361156e8b80@arm.com>
Date: Wed, 12 Nov 2025 17:21:07 +0000
From: Ben Horgan <ben.horgan@....com>
To: Jonathan Cameron <jonathan.cameron@...wei.com>
Cc: james.morse@....com, amitsinght@...vell.com, baisheng.gao@...soc.com,
 baolin.wang@...ux.alibaba.com, bobo.shaobowang@...wei.com,
 carl@...amperecomputing.com, catalin.marinas@....com, dakr@...nel.org,
 dave.martin@....com, david@...hat.com, dfustini@...libre.com,
 fenghuay@...dia.com, gregkh@...uxfoundation.org, gshan@...hat.com,
 guohanjun@...wei.com, jeremy.linton@....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,
 lpieralisi@...nel.org, peternewman@...gle.com, quic_jiles@...cinc.com,
 rafael@...nel.org, robh@...nel.org, rohit.mathew@....com,
 scott@...amperecomputing.com, sdonthineni@...dia.com, sudeep.holla@....com,
 tan.shaopeng@...itsu.com, will@...nel.org, xhao@...ux.alibaba.com,
 Shaopeng Tan <tan.shaopeng@...fujitsu.com>
Subject: Re: [PATCH 11/33] arm_mpam: Add the class and component structures
 for firmware described ris

Hi Jonathan,

On 11/10/25 17:10, Jonathan Cameron wrote:
> On Fri,  7 Nov 2025 12:34:28 +0000
> Ben Horgan <ben.horgan@....com> wrote:
> 
>> From: James Morse <james.morse@....com>
>>
>> An MSC is a container of resources, each identified by their RIS index.
>> Some RIS are described by firmware to provide their position in the system.
>> Others are discovered when the driver probes the hardware.
>>
>> To configure a resource it needs to be found by its class, e.g. 'L2'.
>> There are two kinds of grouping, a class is a set of components, which
>> are visible to user-space as there are likely to be multiple instances
>> of the L2 cache. (e.g. one per cluster or package)
>>
>> Add support for creating and destroying structures to allow a hierarchy
>> of resources to be created.
>>
>> CC: Ben Horgan <ben.horgan@....com>
> Hi Ben,
> 
> Remember to clear out CC'ing yourself.
> 
>> Tested-by: Fenghua Yu <fenghuay@...dia.com>
>> Tested-by: Shaopeng Tan <tan.shaopeng@...fujitsu.com>
>> Tested-by: Peter Newman <peternewman@...gle.com>
>> Signed-off-by: James Morse <james.morse@....com>
>> Signed-off-by: Ben Horgan <ben.horgan@....com>
>> ---
>> Changes since v3:
>> Jonathan:
>> Code reordering.
> 
> I'm guessing I may have sent things in a slightly less than ideal directly.
> 
> Why can't we have ordering as follows (with no forwards declarations)
> 
> mpam_class_alloc()
> mpam_class_destroy()
> //maybe other mpam_class stuff here
> mpam_component_alloc()
> mpam_component_destroy() - needs mpam_class_destroy()
> //maybe other mpam_component stuff here
> mpam_vmsc_alloc()
> mpam_vmsc_destroy() - needs mpam_component_destroy()
> //other mpam_vmsc here

This works and then I need to add mpam_ris_get_affinity() as
mpam_ris_create_locked() depends on it.

I also add the helper functions it depends on
mpam_get_cpumask_from_cache_id() and get_cpumask_from_node_id().

> mpam_ris_create_locked() - needs all the destroys.
> mpam_ris_destroy() - needs mpam vmsc_destroy()

> 
> I may well have missed a more complex dependency chain.
> 
> Other than that, LGTM. Given any change in ordering can be trivially verified
> by building it and Gavin's comments seem simple to resolve.
> 
> Reviewed-by: Jonathan Cameron <jonathan.cameron@...wei.com>

Thanks,

Ben