linux-kernel - Re: [PATCH v22 15/18] x86/resctrl: Make __mon_event

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Date: Fri, 28 Jun 2024 13:56:49 -0700
From: Reinette Chatre <reinette.chatre@...el.com>
To: Tony Luck <tony.luck@...el.com>, Fenghua Yu <fenghua.yu@...el.com>, Maciej
 Wieczor-Retman <maciej.wieczor-retman@...el.com>, Peter Newman
	<peternewman@...gle.com>, James Morse <james.morse@....com>, Babu Moger
	<babu.moger@....com>, Drew Fustini <dfustini@...libre.com>, Dave Martin
	<Dave.Martin@....com>
CC: <x86@...nel.org>, <linux-kernel@...r.kernel.org>,
	<patches@...ts.linux.dev>
Subject: Re: [PATCH v22 15/18] x86/resctrl: Make __mon_event_count() handle
 sum domains

Hi Tony,

On 6/27/24 1:38 PM, Tony Luck wrote:
> Legacy resctrl monitor files must provide the sum of event values across
> all Sub-NUMA Cluster (SNC) domains that share an L3 cache instance.
> 
> There are now two cases:
> 1) A specific domain is provided in struct rmid_read
>     This is either a non-SNC system, or the request is to read data
>     from just one SNC node.
> 2) Domain pointer is NULL. In this case the cacheinfo field in struct
>     rmid_read indicates that all SNC nodes that share that L3 cache
>     instance should have the event read and return the sum of all
>     values.
> 
> Update the CPU sanity check. The existing check that an event is read
> from a CPU in the requested domain still applies when reading a single
> domain. But when summing across domains a more relaxed check that the
> current CPU is in the scope of the L3 cache instance is appropriate
> since the MSRs to read events are scoped at L3 cache level.
> 
> Signed-off-by: Tony Luck <tony.luck@...el.com>
> ---

Reviewed-by: Reinette Chatre <reinette.chatre@...el.com>

Reinette