linux-kernel - Re: [PATCH v9 03/10] x86,fs/resctrl: Detect io

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Message-ID: <13a1d78b-4bcd-4216-93cd-b95961a12369@intel.com>
Date: Wed, 17 Sep 2025 22:15:04 -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>,
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	<linux-doc@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<linux-coco@...ts.linux.dev>, <kvm@...r.kernel.org>
Subject: Re: [PATCH v9 03/10] x86,fs/resctrl: Detect io_alloc feature

Hi Babu,

On 9/2/25 3:41 PM, Babu Moger wrote:
> Smart Data Cache Injection (SDCI) is a mechanism that enables direct
> insertion of data from I/O devices into the L3 cache. It can reduce the
> demands on DRAM bandwidth and reduces latency to the processor consuming
> the I/O data.

This copy&pasted text found in cover letter and patch 1 and now here seems to be the
type of annoying repetitive text that Boris referred to [1]. Looking at this changelog
again it may also be confusing to start with introduction of one feature (SDCI), but
end with another SDCIAE.

Here is a changelog that attempts to address issues, please feel free to improve:

	AMD's SDCIAE (SDCI Allocation Enforcement) PQE feature enables system software  
	to control the portions of L3 cache used for direct insertion of data from   
	I/O devices into the L3 cache.                                                  
                                                                                
	Introduce a generic resctrl cache resource property "io_alloc_capable" as the
	first part of the new "io_alloc" resctrl feature that will support AMD's
	SDCIAE.	Any architecture can set a cache resource as "io_alloc_capable" if a
	portion	of the cache can be allocated for I/O traffic.  
                                                                                
	Set the "io_alloc_capable" property for the L3 cache resource on x86       
	(AMD) systems that support SDCIAE.                          

 
> Introduce cache resource property "io_alloc_capable" that an architecture
> can set if a portion of the cache can be allocated for I/O traffic.
> 
> Set this property on x86 systems that support SDCIAE (L3 Smart Data Cache
> Injection Allocation Enforcement). This property is set only for the L3
> cache resource on systems that support SDCIAE.
> 
> Signed-off-by: Babu Moger <babu.moger@....com>
> Reviewed-by: Reinette Chatre <reinette.chatre@...el.com>
> ---

Reinette


[1] https://lore.kernel.org/lkml/20250911150850.GAaMLmAoi5fTIznQzY@fat_crate.local/