linux-kernel - Re: [PATCH v5 27/29] fs/resctrl: Add file system mechanism for architecture info file

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Message-ID: <aEh-AbZ8N_WZqogb@agluck-desk3>
Date: Tue, 10 Jun 2025 11:48:33 -0700
From: "Luck, Tony" <tony.luck@...el.com>
To: Reinette Chatre <reinette.chatre@...el.com>
Cc: Fenghua Yu <fenghuay@...dia.com>,
	"Wieczor-Retman, Maciej" <maciej.wieczor-retman@...el.com>,
	Peter Newman <peternewman@...gle.com>,
	James Morse <james.morse@....com>, Babu Moger <babu.moger@....com>,
	Drew Fustini <dfustini@...libre.com>,
	Dave Martin <Dave.Martin@....com>,
	"Keshavamurthy, Anil S" <anil.s.keshavamurthy@...el.com>,
	"Chen, Yu C" <yu.c.chen@...el.com>,
	"x86@...nel.org" <x86@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"patches@...ts.linux.dev" <patches@...ts.linux.dev>
Subject: Re: [PATCH v5 27/29] fs/resctrl: Add file system mechanism for
 architecture info file

On Mon, Jun 09, 2025 at 05:30:34PM -0700, Reinette Chatre wrote:
> This should be a directory, a directory owned by the arch where it can create
> debug infrastructure required by arch. The directory name chosen and
> assigned by resctrl fs, while arch has freedom to create more directories
> and add files underneath it. Goal is to isolate all arch specific debug to
> a known location.
> 
> Again, we need to prepare for resctrl fs to potentially use debugfs for its own
> debug and when it does this the expectation is that the layout will mirror
> /sys/fs/resctrl. Creating a directory /sys/kernel/debug/resctrl/info/<rdt_resource::name>_MON
> and then handing it off to the arch goes *against* this. It gives arch
> control over a directory that should be owned by resctrl fs.
> 
> What I have been trying to propose is that resctrl fs create a directory
> /sys/kernel/debug/resctrl/info/<rdt_resource::name>_MON/arch_debug_name_TBD and hand
> a dentry pointer to it to the arch where it can do what is needed to support its debugging needs.
> Isn't this exactly what I wrote in the snippet above? Above you respond with
> statement that you were under impression that it was a directory ... and then
> send a patch that does something else. I am so confused. Gaslighting is
> beneath you.

For the precise name of the "arch_debug_name_TBD" directory, is simply "arch"
sufficient? That leaves every other name available for resctrl
filesystem code free choice if it does add some debug files here.

Or would $ARCH ("x86" in my case) be better to keep distinct debug name
spaces between architectures?

-Tony