linux-kernel - Re: [PATCH v7 04/10] x86,fs/resctrl: Implement "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: <09d7e417-0482-4172-b110-417c12558481@intel.com>
Date: Mon, 21 Jul 2025 16:32:19 -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 04/10] x86,fs/resctrl: Implement "io_alloc"
 enable/disable handlers

Hi Babu,

On 7/10/25 10:16 AM, Babu Moger wrote:
> "io_alloc" enables direct insertion of data from I/O devices into the
> cache.
> 
> On AMD systems, "io_alloc" feature is backed by L3 Smart Data Cache
> Injection Allocation Enforcement (SDCIAE). Change SDCIAE state by setting
> (to enable) or clearing (to disable) bit 1 of MSR L3_QOS_EXT_CFG on all
> logical processors within the cache domain.
> 
> Introduce architecture-specific call to enable and disable the feature.
> 
> The SDCIAE feature details are available in APM listed below [1].
> [1] AMD64 Architecture Programmer's Manual Volume 2: System Programming
> Publication # 24593 Revision 3.41 section 19.4.7 L3 Smart Data Cache
> Injection Allocation Enforcement (SDCIAE)
> 
> Link: https://bugzilla.kernel.org/show_bug.cgi?id=206537
> Signed-off-by: Babu Moger <babu.moger@....com>
> ---

...

>  
> diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> index 885026468440..c165ac333336 100644
> --- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> +++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c

The code looks good to me but rdtgroup.c is becoming bloated by being the default place for
any resctrl changes. While I do know there are counter examples (and I admit I do
not have a clear understanding of original intent) ctrlmondata.c is documented and supported
by its content as the place for cache allocation code. Could you please move these changes
to arch/x86/kernel/cpu/resctrl/ctrlmondata.c? I will try to highlight the other places where
I believe the either fs/resctrl/ctrlmondata.c or arch/x86/kernel/cpu/resctrl/ctrlmondata.c is
more appropriate but please as a high level consider where appropriate to move the IO alloc
code to be with the rest of the cache allocation code. Looking at the series it will help keep
a couple of existing static functions static and keep data structures local to cache allocation
code.

Reinette