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Date: Tue, 16 Apr 2024 17:16:23 +0100
From: Dave Martin <Dave.Martin@arm.com>
To: Reinette Chatre <reinette.chatre@intel.com>
Cc: James Morse <james.morse@arm.com>, x86@kernel.org,
	linux-kernel@vger.kernel.org, Fenghua Yu <fenghua.yu@intel.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
	H Peter Anvin <hpa@zytor.com>, Babu Moger <Babu.Moger@amd.com>,
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	D Scott Phillips OS <scott@os.amperecomputing.com>,
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	Xin Hao <xhao@linux.alibaba.com>, peternewman@google.com,
	dfustini@baylibre.com, amitsinght@marvell.com,
	David Hildenbrand <david@redhat.com>,
	Rex Nie <rex.nie@jaguarmicro.com>
Subject: Re: [PATCH v1 04/31] x86/resctrl: Add helper for setting CPU default
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References: <20240321165106.31602-1-james.morse@arm.com>
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In-Reply-To: <6469d1c9-f535-45e8-91b7-992175cf4697@intel.com>

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