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

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Message-ID: <20260205165837.00007a46@huawei.com>
Date: Thu, 5 Feb 2026 16:58:37 +0000
From: Jonathan Cameron <jonathan.cameron@...wei.com>
To: Ben Horgan <ben.horgan@....com>
CC: <amitsinght@...vell.com>, <baisheng.gao@...soc.com>,
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Subject: Re: [PATCH v4 28/41] arm_mpam: resctrl: Pick classes for use as mbm
 counters

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

> From: James Morse <james.morse@....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@....com>
> Signed-off-by: Ben Horgan <ben.horgan@....com>

Seems fine to me.

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