linux-kernel - Re: [PATCH v1 04/31] x86/resctrl: Add helper for setting CPU default properties

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Date: Mon, 15 Apr 2024 10:45:07 -0700
From: Reinette Chatre <reinette.chatre@...el.com>
To: Dave Martin <Dave.Martin@....com>
CC: James Morse <james.morse@....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>, <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>,
	David Hildenbrand <david@...hat.com>, Rex Nie <rex.nie@...uarmicro.com>
Subject: Re: [PATCH v1 04/31] x86/resctrl: Add helper for setting CPU default
 properties

Hi Dave,

On 4/12/2024 9:13 AM, Dave Martin wrote:
> On Mon, Apr 08, 2024 at 08:15:03PM -0700, Reinette Chatre wrote:
>> Hi James,
>>
>> On 3/21/2024 9:50 AM, James Morse wrote:
>>
>>> --- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
>>> +++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
>>> @@ -3623,14 +3623,18 @@ static int rdtgroup_mkdir(struct kernfs_node *parent_kn, const char *name,
>>>  static int rdtgroup_rmdir_mon(struct rdtgroup *rdtgrp, cpumask_var_t tmpmask)
>>>  {
>>>  	struct rdtgroup *prdtgrp = rdtgrp->mon.parent;
>>> +	u32 closid, rmid;
>>>  	int cpu;
>>>  
>>>  	/* Give any tasks back to the parent group */
>>>  	rdt_move_group_tasks(rdtgrp, prdtgrp, tmpmask);
>>>  
>>>  	/* Update per cpu rmid of the moved CPUs first */
>>> +	closid = rdtgrp->closid;
>>> +	rmid = prdtgrp->mon.rmid;
>>>  	for_each_cpu(cpu, &rdtgrp->cpu_mask)
>>> -		per_cpu(pqr_state.default_rmid, cpu) = prdtgrp->mon.rmid;
>>> +		resctrl_arch_set_cpu_default_closid_rmid(cpu, closid, rmid);
>>> +
>>
>> While I understand that the CLOSIDs are the same, I do think it looks unexpected
>> for the CLOSID to be set to the CLOSID of the group being removed. Could this
>> be set to CLOSID of parent group instead?
>>
>> Reinette
> 
> That seems reasonable.  How about something like this?
> 
> -	closid = rdtgrp->closid;
> +	closid = prdtgrp->closid; /* no change, but the arch code needs it */

Looks good. If the comment stays, please do replace the tail comment with a
freestanding comment (for reference you can search for "No tail comments"
in Documentation/process/maintainer-tip.rst). 

Thank you

Reinette