Re: [RFC PATCH v2 00/10] arm_mpam: resctrl: Separate MPAM domains

[Reinette Chatre <reinette.chatre@intel.com>]

Hi Jinjie,

On 10/26/26 8:42 PM, Jinjie Ruan wrote:
> 
> 
> 在 2026/10/20 6:07, Reinette Chatre 写道:
>> RFC v1: https://lore.kernel.org/lkml/85ca29e89eacf12cfa7071249419e7cadb8f0691.1788220029.git.reinette.chatre@intel.com/
>>
>> The MPAM driver represents a resctrl domain with a single structure,
>> struct mpam_resctrl_dom, that holds both a control domain and a
>> monitoring domain. On a system that supports both allocation and
>> monitoring, one instance is created for each domain and its two
>> domains are added to the resource's control and monitoring domain
>> lists.
>>
>> Holding both domains in one structure requires control and monitoring
>> to be done at the same scope, and ties each control domain to a
>> monitoring domain. This does not fit the proposed support for multiple
>> controls per resource [1]. There, each control of a resource, for
>> example a "min" and a "max" memory bandwidth control, has its own list
>> of control domains while the resource keeps a single list of
>> monitoring domains. With one structure for both, every control domain
>> would come with a monitoring domain of its own, which does not reflect
>> the resource.
>>
>> This series gives control and monitoring domains their own structures,
>> set up and torn down independently as CPUs come online and go offline,
>> in preparation for supporting multiple controls per resource. Along
>> the way it stops failing CPU online when a domain cannot be set up,
>> and adds checks when setting up a monitoring domain.
>>
>>   1-2   Preparatory cleanups of domain allocation
>>   3     Do not fail CPU online when domain setup fails
>>   4-6   Separate the control and monitoring domain structures
>>   7-9   Checks when setting up a monitoring domain
>>   10    Comment update, kept separate for review
>>
>> An earlier version of the domain split was posted on its own [2]. This
>> version incorporates the feedback from that discussion. It gives each
>> type of domain its own structure instead of duplicating the shared
>> one, sets up each domain independently instead of undoing one domain
>> when setting up the other fails, and adds the checks in patches 8 and
>> 9.
>>
>> Patch 7 turns a WARN_ON_ONCE(0) into a warning that fires. It is a
>> separate patch because it is not clear whether the silent failure was
>> intended. If it was, the patch can instead drop the dead
>> WARN_ON_ONCE().
>>
>> This is an RFC because I am only able to compile test MPAM changes,
>> which is also why the patches are small and each change is justified
>> on its own. Patches can be squashed if preferred, for example patch 10
>> into patches 5 and 9. Testing on MPAM hardware would be greatly
>> appreciated, as is any other feedback.
> 
> Hi Reinette,
> 
> I tested it on a QEMU with MPAM rebased on v7.3-rc6 and all pass:
> 
> 1、Resctrl mounts，L3/L2 each report 32 closids (control IDs)
> 2、Cache and memory bandwidth controls
> 3、Priority, min, max, option and hard-limit: write, read back, and the
> 
>    emulated hardware shows the same value
> 4、CDP mode and usage/bandwidth counters
> 5、All builds pass without warnings: arm64/x86_64, debug on/off,
>    self-tests on/off, resctrl off, ACPI off
> 
> Test cases: https://github.com/ruanjinjie-eng/mpam_testcase/tree/qemu
> 
> Tested-by: Jinjie Ruan ruanjinjie@huawei.com
Thank you very much for this thorough testing. It is much appreciated.

Reinette