linux-kernel - Re: [PATCH v7 09/10] fs/resctrl: Modify rdt_parse

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Message-ID: <798ba4db-3ac2-44a9-9e0d-e9cbb0dbff45@intel.com>
Date: Mon, 21 Jul 2025 20:30:41 -0700
From: Reinette Chatre <reinette.chatre@...el.com>
To: Babu Moger <babu.moger@....com>, <corbet@....net>, <tony.luck@...el.com>,
	<Dave.Martin@....com>, <james.morse@....com>, <tglx@...utronix.de>,
	<mingo@...hat.com>, <bp@...en8.de>, <dave.hansen@...ux.intel.com>
CC: <x86@...nel.org>, <hpa@...or.com>, <akpm@...ux-foundation.org>,
	<paulmck@...nel.org>, <rostedt@...dmis.org>, <Neeraj.Upadhyay@....com>,
	<david@...hat.com>, <arnd@...db.de>, <fvdl@...gle.com>, <seanjc@...gle.com>,
	<thomas.lendacky@....com>, <pawan.kumar.gupta@...ux.intel.com>,
	<yosry.ahmed@...ux.dev>, <sohil.mehta@...el.com>, <xin@...or.com>,
	<kai.huang@...el.com>, <xiaoyao.li@...el.com>, <peterz@...radead.org>,
	<me@...aill.net>, <mario.limonciello@....com>, <xin3.li@...el.com>,
	<ebiggers@...gle.com>, <ak@...ux.intel.com>, <chang.seok.bae@...el.com>,
	<andrew.cooper3@...rix.com>, <perry.yuan@....com>,
	<linux-doc@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v7 09/10] fs/resctrl: Modify rdt_parse_data to pass mode
 and CLOSID

Hi Babu,

On 7/10/25 10:16 AM, Babu Moger wrote:
> The functions parse_cbm() and parse_bw() require mode and CLOSID to

No need to say "function" when using (). Also, drop parse_bw(), since it
does not validate CBMs.

> validate the Capacity Bit Mask (CBM). It is passed through struct

"passed through" -> "passed via"?

> rdtgroup in rdt_parse_data.

"rdt_parse_data" -> "struct rdt_parse_data"

> 
> This can be simplified by passing the mode and closid directly, instead of

closid -> CLOSID

> through the rdtgroup struct. Doing so also facilitates calling parse_cbm()
> to verify the CBM within the io_alloc feature, since io_alloc does not
> have rdtgroup context.

Above notes that "simplification" is the primary motivation but I do not think
this change qualifies as a "simplification". How about second paragraph changed
to something like:

	The io_alloc feature also uses CBMs to indicate which portions of
	cache are allocated for I/O traffic. The CBMs are provided by
	user space and need to be validated the same as CBMs provided for
	general (CPU) cache allocation. parse_cbm() cannot be used as-is
	since io_alloc does not have rdtgroup context.

	Pass the mode and CLOSID directly to parse_cbm() via struct rdt_parse_data
	instead of through the rdtgroup struct to facilitate calling parse_cbm() to
	verify the CBM of the io_alloc feature.

(please feel free to improve)

> 
> Signed-off-by: Babu Moger <babu.moger@....com>
> ---



> ---
>  fs/resctrl/ctrlmondata.c | 29 +++++++++++++----------------
>  fs/resctrl/internal.h    |  6 ++++++
>  2 files changed, 19 insertions(+), 16 deletions(-)
> 
> diff --git a/fs/resctrl/ctrlmondata.c b/fs/resctrl/ctrlmondata.c
> index e78828b0408a..5c16557fb7a8 100644
> --- a/fs/resctrl/ctrlmondata.c
> +++ b/fs/resctrl/ctrlmondata.c
> @@ -23,11 +23,6 @@
>  
>  #include "internal.h"
>  
> -struct rdt_parse_data {
> -	struct rdtgroup		*rdtgrp;
> -	char			*buf;
> -};
> -

This patch is only about replacing rdtgroup with mode and CLOSID, there is no
motivation for relocating the structure declaration. This looks to be a change
needed by following patch but is another change that becomes unnecessary if
the io_alloc code, specifically resctrl_io_alloc_cbm_write() and
resctrl_io_alloc_parse_line() from next patch, are moved to ctrlmondata.c.

...

> @@ -171,7 +167,7 @@ static int parse_cbm(struct rdt_parse_data *data, struct resctrl_schema *s,
>  	 * Cannot set up more than one pseudo-locked region in a cache
>  	 * hierarchy.
>  	 */
> -	if (rdtgrp->mode == RDT_MODE_PSEUDO_LOCKSETUP &&
> +	if (mode == RDT_MODE_PSEUDO_LOCKSETUP &&
>  	    rdtgroup_pseudo_locked_in_hierarchy(d)) {
>  		rdt_last_cmd_puts("Pseudo-locked region in hierarchy\n");
>  		return -EINVAL;
> @@ -180,9 +176,9 @@ static int parse_cbm(struct rdt_parse_data *data, struct resctrl_schema *s,
>  	if (!cbm_validate(data->buf, &cbm_val, r))
>  		return -EINVAL;
>  
> -	if ((rdtgrp->mode == RDT_MODE_EXCLUSIVE ||
> -	     rdtgrp->mode == RDT_MODE_SHAREABLE) &&
> -	    rdtgroup_cbm_overlaps_pseudo_locked(d, cbm_val)) {
> +	if ((mode == RDT_MODE_EXCLUSIVE ||
> +	     mode == RDT_MODE_SHAREABLE) &&
> +	     rdtgroup_cbm_overlaps_pseudo_locked(d, cbm_val)) {

Please fix alignment.

>  		rdt_last_cmd_puts("CBM overlaps with pseudo-locked region\n");
>  		return -EINVAL;
>  	}

Reinette