Re: [PATCH v4 28/41] arm_mpam: resctrl: Pick classes for use as mbm counters

Jonathan Cameron
2026-02-05T16:58:42Z

On Tue, 3 Feb 2026 21:43:29 +0000
Ben Horgan <ben.horgan@arm.com> wrote:

> From: James Morse <james.morse@arm.com>
>
> resctrl has two types of counters, NUMA-local and global. MPAM can only
> count global either using MSC at the L3 cache or in the memory controllers.
> When global and local equate to the same thing continue just to call it
> global.
>
> Because the class or component backing the event may not be 'the L3', it is
> necessary for mpam_resctrl_get_domain_from_cpu() to search the monitor
> domains too. This matters the most for 'monitor only' systems, where 'the
> L3' control domains may be empty, and the ctrl_comp pointer NULL.
>
> resctrl expects there to be enough monitors for every possible control and
> monitor group to have one. Such a system gets called 'free running' as the
> monitors can be programmed once and left running. Any other platform will
> need to emulate ABMC.
>
> Signed-off-by: James Morse <james.morse@arm.com>
> Signed-off-by: Ben Horgan <ben.horgan@arm.com>

Seems fine to me.

Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>