linux-kernel - Re: [PATCH v9 10/10] fs/resctrl: Update bit_usage to reflect io

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <79b2d040-a3e6-40db-b545-bb07d42c8c29@intel.com>
Date: Wed, 17 Sep 2025 23:08:53 -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>, <kas@...nel.org>,
	<rick.p.edgecombe@...el.com>, <akpm@...ux-foundation.org>,
	<paulmck@...nel.org>, <pmladek@...e.com>,
	<pawan.kumar.gupta@...ux.intel.com>, <rostedt@...dmis.org>,
	<kees@...nel.org>, <arnd@...db.de>, <fvdl@...gle.com>, <seanjc@...gle.com>,
	<thomas.lendacky@....com>, <manali.shukla@....com>, <perry.yuan@....com>,
	<sohil.mehta@...el.com>, <xin@...or.com>, <peterz@...radead.org>,
	<mario.limonciello@....com>, <gautham.shenoy@....com>, <nikunj@....com>,
	<dapeng1.mi@...ux.intel.com>, <ak@...ux.intel.com>,
	<chang.seok.bae@...el.com>, <ebiggers@...gle.com>,
	<linux-doc@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<linux-coco@...ts.linux.dev>, <kvm@...r.kernel.org>
Subject: Re: [PATCH v9 10/10] fs/resctrl: Update bit_usage to reflect io_alloc

Hi Babu,

On 9/2/25 3:41 PM, Babu Moger wrote:
> When the io_alloc feature is enabled, a portion of the cache can be
> configured for shared use between hardware and software.

(repetitive)

> 
> Update bit_usage representation to reflect the io_alloc configuration.
> Revise the documentation for "shareable_bits" and "bit_usage" to reflect
> the impact of io_alloc feature.

Attempt at new version, please feel free to improve:

	The "shareable_bits" and "bit_usage" resctrl files associated with cache
	resources give insight into how instances of a cache is used.                  
                                                                                
	Update the annotated capacity bitmasks displayed by "bit_usage" to include the  
	cache portions allocated for I/O via the "io_alloc" feature. "shareable_bits" is
	a global bitmask of shareable cache with I/O and can thus not present the
	per-domain I/O allocations possible with the "io_alloc" feature. Revise the
	"shareable_bits" documentation to direct users to "bit_usage" for accurate
	cache usage information.                                                                    

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

...

> ---
>  Documentation/filesystems/resctrl.rst | 35 ++++++++++++++++-----------
>  fs/resctrl/ctrlmondata.c              |  2 +-
>  fs/resctrl/internal.h                 |  2 ++
>  fs/resctrl/rdtgroup.c                 | 21 ++++++++++++++--
>  4 files changed, 43 insertions(+), 17 deletions(-)
> 
> diff --git a/Documentation/filesystems/resctrl.rst b/Documentation/filesystems/resctrl.rst
> index 7e3eda324de5..72ea6f3f36bc 100644
> --- a/Documentation/filesystems/resctrl.rst
> +++ b/Documentation/filesystems/resctrl.rst
> @@ -90,12 +90,19 @@ related to allocation:
>  		must be set when writing a mask.
>  
>  "shareable_bits":
> -		Bitmask of shareable resource with other executing
> -		entities (e.g. I/O). User can use this when
> -		setting up exclusive cache partitions. Note that
> -		some platforms support devices that have their
> -		own settings for cache use which can over-ride
> -		these bits.
> +		Bitmask of shareable resource with other executing entities
> +		(e.g. I/O). Applies to all instances of this resource. User
> +		can use this when setting up exclusive cache partitions.
> +		Note that some platforms support devices that have their
> +		own settings for cache use which can over-ride these bits.
> +
> +		When "io_alloc" is enabled, a portion of each cache instance can
> +		be configured for shared use between hardware and software.
> +		"bit_usage" should be used to see which portions of each cache
> +		instance is configured for hardware use via "io_alloc" feature
> +		because every cache instance can have its "io_alloc" bitmask
> +		configured independently via io_alloc_cbm.

io_alloc_cbm -> "io_alloc_cbm" (to consistently place names of resctrl files in quotes)

> +
>  "bit_usage":
>  		Annotated capacity bitmasks showing how all
>  		instances of the resource are used. The legend is:
> @@ -109,16 +116,16 @@ related to allocation:
>  			"H":
>  			      Corresponding region is used by hardware only
>  			      but available for software use. If a resource
> -			      has bits set in "shareable_bits" but not all
> -			      of these bits appear in the resource groups'
> -			      schematas then the bits appearing in
> -			      "shareable_bits" but no resource group will
> -			      be marked as "H".
> +			      has bits set in "shareable_bits" or "io_alloc_cbm"
> +			      but not all of these bits appear in the resource
> +			      groups' schematas then the bits appearing in

I understand that you are just copying this but "schemata" is plural of "schema". Since you
are copying this text, could you please fix "schematas" to be "schemata" while doing so?


> +			      "shareable_bits" or "io_alloc_cbm" but no
> +			      resource group will be marked as "H".
>  			"X":
>  			      Corresponding region is available for sharing and
> -			      used by hardware and software. These are the
> -			      bits that appear in "shareable_bits" as
> -			      well as a resource group's allocation.
> +			      used by hardware and software. These are the bits
> +			      that appear in "shareable_bits" or "io_alloc_cbm"
> +			      as well as a resource group's allocation.
>  			"S":
>  			      Corresponding region is used by software
>  			      and available for sharing.

Reinette