linux-kernel - Re: [PATCH v2 07/18] x86/resctrl: Move CLOSID/RMID matching and setting to use helpers

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Message-ID: <CALPaoCjP4Zx9-QUOJwZEQ_5acFhgkr+9TND3mqUvefQmgkbqCw@mail.gmail.com>
Date:   Wed, 8 Mar 2023 11:30:21 +0100
From:   Peter Newman <peternewman@...gle.com>
To:     James Morse <james.morse@....com>
Cc:     Reinette Chatre <reinette.chatre@...el.com>, x86@...nel.org,
        linux-kernel@...r.kernel.org, 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>
Subject: Re: [PATCH v2 07/18] x86/resctrl: Move CLOSID/RMID matching and
 setting to use helpers

Hi James,

On Mon, Mar 6, 2023 at 12:32 PM James Morse <james.morse@....com> wrote:
> On 02/02/2023 23:47, Reinette Chatre wrote:
> > On 1/13/2023 9:54 AM, James Morse wrote:
> >> +    resctrl_arch_set_closid_rmid(tsk, rdtgrp->closid, rdtgrp->mon.rmid);
> >
> > This does not use the intended closid when rdtgrp->type == RDTMON_GROUP.
>
> Yes, it should be rdtgrp->mon.parent->closid.
>
> rdtgroup_mkdir_mon() initialises them to be the same, I guess its Peter's monitor-group
> rename that means this could get the wrong value?

I noticed this earlier. The next revision of my MON group rename patch
series updates rdtgrp->closid to that of the new parent so that for
MON groups, rdtgrp->closid == rdtgrp->mon.parent->closid continues to
hold.

It looks like rdt_move_group_tasks() assumes this, as it always sets
t->closid to rdtgrp->closid.

-Peter