linux-kernel - Re: [PATCH v2 22/35] x86/resctrl: Make resctrl_arch_pseudo_lock

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Message-ID: <8d3b27d9-1a58-455d-aaa7-ff9a7e49a0b2@arm.com>
Date: Fri, 14 Jun 2024 14:58:08 +0100
From: James Morse <james.morse@....com>
To: Dave Martin <Dave.Martin@....com>, x86@...nel.org,
 linux-kernel@...r.kernel.org
Cc: Fenghua Yu <fenghua.yu@...el.com>,
 Reinette Chatre <reinette.chatre@...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,
 D Scott Phillips OS <scott@...amperecomputing.com>,
 carl@...amperecomputing.com, lcherian@...vell.com,
 bobo.shaobowang@...wei.com, "Shaopeng Tan (Fujitsu)"
 <tan.shaopeng@...itsu.com>, baolin.wang@...ux.alibaba.com,
 Jamie Iles <quic_jiles@...cinc.com>, Xin Hao <xhao@...ux.alibaba.com>,
 Peter Newman <peternewman@...gle.com>, dfustini@...libre.com,
 amitsinght@...vell.com, David Hildenbrand <david@...hat.com>,
 Rex Nie <rex.nie@...uarmicro.com>
Subject: Re: [PATCH v2 22/35] x86/resctrl: Make resctrl_arch_pseudo_lock_fn()
 take a plr

Hi Dave,

On 26/04/2024 16:08, Dave Martin wrote:
> From: James Morse <james.morse@....com>
> 
> resctrl_arch_pseudo_lock_fn() has architecture specific behaviour,
> and takes a struct rdtgroup as an argument.
> 
> After the filesystem code moves to /fs/, the definition of struct
> rdtgroup will not be available to the architecture code.
> 
> The only reason resctrl_arch_pseudo_lock_fn() wants the rdtgroup is
> for the CLOSID. Embed that in the pseudo_lock_region as a closid,
> and move the definition of struct pseudo_lock_region to resctrl.h.

> FYI: James Morse:
> 
>  * Review the v2 change below, in case there was any functional reason
>    for distinguishing "hw" closids here.
> 
> Changes in v2:
> 
>  * [Commit message only] Typo fix:
>    s/hw_closid/closid/g
> 
>    (The name "closid" is used in the code.  If there is a distinction
>    between "hardware" closids and resctrl closids, it doesn't seem to
>    be explicit in the naming elsewhere.)

Heh, this is a blast from the past!

In 2018 I was trying to get resctrl to convert 'closid' to 'hw_closid' using some
architecture provided helpers. This was an alternative way of folding the CDP code to hide
the differences between x86/arm64. I decided the fs/resctrl code was cleaner without it -
and arm64 can just juggle the numbers instead.


Thanks,

James