linux-kernel - Re: [PATCH v2 06/24] x86/resctrl: Walk the resctrl schema list instead of an arch list

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Message-ID: <aad608d2-660d-89b9-5191-551ad8b0c66d@intel.com>
Date:   Wed, 31 Mar 2021 14:38:40 -0700
From:   Reinette Chatre <reinette.chatre@...el.com>
To:     James Morse <james.morse@....com>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Cc:     Fenghua Yu <fenghua.yu@...el.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        H Peter Anvin <hpa@...or.com>,
        Babu Moger <Babu.Moger@....com>,
        shameerali.kolothum.thodi@...wei.com,
        Jamie Iles <jamie@...iainc.com>,
        D Scott Phillips OS <scott@...amperecomputing.com>
Subject: Re: [PATCH v2 06/24] x86/resctrl: Walk the resctrl schema list
 instead of an arch list

Hi James,

On 3/12/2021 9:58 AM, James Morse wrote:
> Once the arch code is abstracted from the resctrl filesystem code
> the separate schema for CDP are created by the filesystem code. This
> means the same resource is used for different schema, or types of
> configuration.
> 
> Helpers like rdtgroup_cbm_overlaps() need the resctrl_schema to
> retrieve the configuration (or configurations). Before these
> helpers can be changed to take the schema instead of the resource,
> their callers must have the schema on hand.
> 
> Change the users of for_each_alloc_enabled_rdt_resource() to walk
> the schema instead. Schema were only created for alloc_enabled resources
> so these two lists are currently equivalent.

Currently equivalent? Does this mean that at some point they will not be 
equivalent and this change will be impacted?

> 
> schemata_list_create() and rdt_kill_sb() are ignored. The first
> creates the schema list, and will eventually loop over the resource
> indexes using an arch helper to retrieve the resource. rdt_kill_sb()
> will eventually make use of an arch 'reset everything' helper.

Please elaborate on what "eventually" means here. It does not seem to 
indicate this patch series so please clarify that and any impacts.

> 
> After the filesystem code is moved, rdtgroup_pseudo_locked_in_hierarchy()
> remains part of the x86 specific hooks to support psuedo lock. This code

psuedo -> pseudo

Thank you

Reinette