linux-kernel - Re: [PATCH v6 19/24] x86/resctrl: Add helpers for system wide mon/alloc capable

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Date:   Tue, 3 Oct 2023 14:19:49 -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>,
        D Scott Phillips OS <scott@...amperecomputing.com>,
        <carl@...amperecomputing.com>, <lcherian@...vell.com>,
        <bobo.shaobowang@...wei.com>, <tan.shaopeng@...itsu.com>,
        <xingxin.hx@...nanolis.org>, <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 v6 19/24] x86/resctrl: Add helpers for system wide
 mon/alloc capable

Hi James,

On 9/14/2023 10:21 AM, James Morse wrote:
> resctrl reads rdt_alloc_capable or rdt_mon_capable to determine
> whether any of the resources support the corresponding features.
> resctrl also uses the static-keys that affect the architecture's
> context-switch code to determine the same thing.
> 
> This forces another architecture to have the same static-keys.
> 
> As the static-key is enabled based on the capable flag, and none of
> the filesystem uses of these are in the scheduler path, move the
> capable flags behind helpers, and use these in the filesystem
> code instead of the static-key.
> 
> After this change, only the architecture code manages and uses
> the static-keys to ensure __resctrl_sched_in() does not need
> runtime checks.
> 
> This avoids multiple architectures having to define the same
> static-keys.
> 
> Cases where the static-key implicitly tested if the resctrl
> filesystem was mounted all have an explicit check added by a
> previous patch.
> 
> Tested-by: Shaopeng Tan <tan.shaopeng@...itsu.com>
> Reviewed-by: Shaopeng Tan <tan.shaopeng@...itsu.com>
> Tested-By: Peter Newman <peternewman@...gle.com>
> Signed-off-by: James Morse <james.morse@....com>
> 
> ---

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

Reinette