linux-kernel - Re: [PATCH v7 16/24] x86/resctrl: Make resctrl

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Message-ID: <bf7c1a04-0a55-6d02-7c5d-5db3293b0e78@arm.com>
Date:   Thu, 14 Dec 2023 11:38:08 +0000
From:   James Morse <james.morse@....com>
To:     babu.moger@....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>,
        shameerali.kolothum.thodi@...wei.com,
        D Scott Phillips OS <scott@...amperecomputing.com>,
        carl@...amperecomputing.com, lcherian@...vell.com,
        bobo.shaobowang@...wei.com, tan.shaopeng@...itsu.com,
        baolin.wang@...ux.alibaba.com, Jamie Iles <quic_jiles@...cinc.com>,
        Xin Hao <xhao@...ux.alibaba.com>, peternewman@...gle.com,
        dfustini@...libre.com, amitsinght@...vell.com
Subject: Re: [PATCH v7 16/24] x86/resctrl: Make resctrl_mounted checks
 explicit

Hi Babu,

On 09/11/2023 20:47, Moger, Babu wrote:
> On 10/25/23 13:03, James Morse wrote:
>> The rdt_enable_key is switched when resctrl is mounted, and used to
>> prevent a second mount of the filesystem. It also enables the
>> architecture's context switch code.
>>
>> This requires another architecture to have the same set of static-keys,
>> as resctrl depends on them too. The existing users of these static-keys
>> are implicitly also checking if the filesystem is mounted.
>>
>> Make the resctrl_mounted checks explicit: resctrl can keep track of
>> whether it has been mounted once. This doesn't need to be combined with
>> whether the arch code is context switching the CLOSID.
>>
>> rdt_mon_enable_key is never used just to test that resctrl is mounted,
>> but does also have this implication. Add a resctrl_mounted to all uses
>> of rdt_mon_enable_key. This will allow rdt_mon_enable_key to be swapped
>> with a helper in a subsequent patch.
>>
>> This will allow the static-key changing to be moved behind resctrl_arch_
>> calls.

> Reviewed-by: Babu Moger <babu.moger@....com>

Thanks!


James