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

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Date:   Fri, 10 Mar 2023 12:00:02 -0800
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>
Subject: Re: [PATCH v2 07/18] x86/resctrl: Move CLOSID/RMID matching and
 setting to use helpers

Hi James,

On 3/6/2023 3:32 AM, James Morse wrote:
> On 02/02/2023 23:47, Reinette Chatre wrote:
>> On 1/13/2023 9:54 AM, James Morse wrote:
>>
>> ...
>>
>>> @@ -567,19 +579,14 @@ static int __rdtgroup_move_task(struct task_struct *tsk,
>>>  	 * For monitor groups, can move the tasks only from
>>>  	 * their parent CTRL group.
>>>  	 */
>>> -
>>> -	if (rdtgrp->type == RDTCTRL_GROUP) {
>>> -		WRITE_ONCE(tsk->closid, rdtgrp->closid);
>>> -		WRITE_ONCE(tsk->rmid, rdtgrp->mon.rmid);
>>> -	} else if (rdtgrp->type == RDTMON_GROUP) {
>>> -		if (rdtgrp->mon.parent->closid == tsk->closid) {
>>> -			WRITE_ONCE(tsk->rmid, rdtgrp->mon.rmid);
>>> -		} else {
>>> -			rdt_last_cmd_puts("Can't move task to different control group\n");
>>> -			return -EINVAL;
>>> -		}
>>> +	if (rdtgrp->type == RDTMON_GROUP &&
>>> +	    !resctrl_arch_match_closid(tsk, rdtgrp->mon.parent->closid)) {
>>> +		rdt_last_cmd_puts("Can't move task to different control group\n");
>>> +		return -EINVAL;
>>>  	}
>>>  
>>> +	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

Even so, I do find the code to be confusing when it jumps from one to
the other within the same function.

>, I guess its Peter's monitor-group
> rename that means this could get the wrong value?
> 
> I've fixed it as:
> ---------%<---------
> diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> index c7392d10dc5b..30d8961b833c 100644
> --- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> +++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> @@ -585,7 +585,12 @@ static int __rdtgroup_move_task(struct task_struct *tsk,
>                 return -EINVAL;
>         }
> 
> -       resctrl_arch_set_closid_rmid(tsk, rdtgrp->closid, rdtgrp->mon.rmid);
> +       if (rdtgrp->type == RDTMON_GROUP)
> +               resctrl_arch_set_closid_rmid(tsk, rdtgrp->mon.parent->closid,
> +                                            rdtgrp->mon.rmid);
> +       else
> +               resctrl_arch_set_closid_rmid(tsk, rdtgrp->closid,
> +                                            rdtgrp->mon.rmid);
> 
>         /*
>          * Ensure the task's closid and rmid are written before determining if
> ---------%<---------
> 
> 

ok, thank you.

Reinette