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

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Date: Tue, 16 Apr 2024 17:16:23 +0100
From: Dave Martin <Dave.Martin@....com>
To: Reinette Chatre <reinette.chatre@...el.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

On Mon, Apr 15, 2024 at 10:45:07AM -0700, Reinette Chatre wrote:
> 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). 

Ack, noted.

Cheers
---Dave