linux-kernel - Re: [PATCH v19 16/20] x86/resctrl: Make resctrl_arch_rmid

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Date: Fri, 7 Jun 2024 09:49:30 -0700
From: Reinette Chatre <reinette.chatre@...el.com>
To: Tony Luck <tony.luck@...el.com>
CC: 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>,
	<x86@...nel.org>, <linux-kernel@...r.kernel.org>, <patches@...ts.linux.dev>
Subject: Re: [PATCH v19 16/20] x86/resctrl: Make resctrl_arch_rmid_read()
 handle sum over domains

Hi Tony,

On 6/3/24 4:15 PM, Tony Luck wrote:
> On Thu, May 30, 2024 at 01:24:57PM -0700, Reinette Chatre wrote:
>> On 5/28/24 3:20 PM, Tony Luck wrote:
...

>>> +
>>> +	return 0;
>>> +}
>>> +
>>> +int resctrl_arch_rmid_read(struct rdt_resource *r, struct rdt_mon_domain *d,
>>> +			   u32 unused, u32 rmid, enum resctrl_event_id eventid,
>>> +			   u64 *val, bool sum, struct cacheinfo *ci, void *ignored)
>>
>> This is not architecture specific code.
> 
> Can you explain further? I've dropped the "sum" argument. As you pointed
> out elsewhere this can be inferred from "d == NULL".  But I do need the
> cacheinfo information in resctrl_arch_rmid_read() to:
> 1) determine which domains to sum (those that match ci->id).
> 2) sanity check code is executing on a CPU in ci->shared_cpu_map.
> 

"resctrl_arch_*" is the prefix of functions needed to be implemented
by every architecture. As I understand there is nothing architecture
specific about what this function does and every architecture's function
would thus end up looking identical. I expected the cacheinfo
information to be available from all architectures. If this is not
the case then it does not belong in struct rdt_mon_domain but should
instead be moved to struct rdt_hw_mon_domain ... but since cacheinfo
has already made its way into the filesystem code it is not clear
to me how you envision the arch/fs split.

Reinette