linux-kernel - Re: [PATCH v2 3/3] x86/resctrl: Add "*" shorthand to set minimum io

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Message-ID: <a76c2eee-2a64-42ab-b81c-90638321cd15@intel.com>
Date: Thu, 18 Dec 2025 14:59:59 -0800
From: Reinette Chatre <reinette.chatre@...el.com>
To: "Luck, Tony" <tony.luck@...el.com>, "Moger, Babu" <bmoger@....com>, "Aaron
 Tomlin" <atomlin@...mlin.com>, "Dave.Martin@....com" <Dave.Martin@....com>,
	"james.morse@....com" <james.morse@....com>, "babu.moger@....com"
	<babu.moger@....com>, "tglx@...utronix.de" <tglx@...utronix.de>,
	"mingo@...hat.com" <mingo@...hat.com>, "bp@...en8.de" <bp@...en8.de>,
	"dave.hansen@...ux.intel.com" <dave.hansen@...ux.intel.com>
CC: "sean@...e.io" <sean@...e.io>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 3/3] x86/resctrl: Add "*" shorthand to set minimum
 io_alloc CBM for all domains

Hi Tony,

On 12/18/25 1:49 PM, Luck, Tony wrote:
>> +       if (id && *id == '*') {
> 
> That will accept arbitrary chars after the "*".
> 
> 	if (id && !strcmp(id, "*"))
> 
>> What do you think?
> 
> Why is io_alloc special? The same simple change could apply to parse_line() to allow
> setting all domains in a resource to be set to the same value:
> 
> # echo "L3:*=fff" > schemata
> 
> # echo "MB:*=50" > schemata

If I remember correctly the idea was to limit this feature to io_alloc to avoid needing
to deal with L2 asymmetric domains [1].

Reinette

[1] https://lore.kernel.org/lkml/SJ1PR11MB60833A27A1B8057CDDFB1B2BFCCFA@SJ1PR11MB6083.namprd11.prod.outlook.com/