linux-kernel - Re: [PATCH v9 01/10] x86/cpufeatures: Add support for L3 Smart Data Cache Injection Allocation Enforcement

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Message-ID: <19fa188a-bd1d-43e6-bed0-1ca35cbf34ac@intel.com>
Date: Wed, 17 Sep 2025 22:08:18 -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>
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	<rick.p.edgecombe@...el.com>, <akpm@...ux-foundation.org>,
	<paulmck@...nel.org>, <pmladek@...e.com>,
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Subject: Re: [PATCH v9 01/10] x86/cpufeatures: Add support for L3 Smart Data
 Cache Injection Allocation Enforcement

Hi Babu,

(Just highlighting some changelog formatting that was needed for ABMC
changelogs.)

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. By directly caching
> data from I/O devices rather than first storing the I/O data in DRAM,
> SDCI reduces demands on DRAM bandwidth and reduces latency to the processor
> consuming the I/O data.
> 
> The SDCIAE (SDCI Allocation Enforcement) PQE feature allows system software
> to control the portion of the L3 cache used for SDCI.
> 
> When enabled, SDCIAE forces all SDCI lines to be placed into the L3 cache
> partitions identified by the highest-supported L3_MASK_n register, where n
> is the maximum supported CLOSID.
> 
> Add CPUID feature bit that can be used to configure SDCIAE.
> 
> The SDCIAE feature details are documented in APM [1] available from [2].
> [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)

Compare with how indentation of ABMC "x86,fs/resctrl: Implement resctrl_arch_config_cntr()
to assign a counter with ABMC" was changed during merge. 

  [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)

(also applies to patch #4)

> 
> Link: https://bugzilla.kernel.org/show_bug.cgi?id=206537 # [2]

Please place "Link:" tag at end to reduce needed adjustments during
merge.

> Signed-off-by: Babu Moger <babu.moger@....com>
> Acked-by: Borislav Petkov (AMD) <bp@...en8.de>
> Reviewed-by: Reinette Chatre <reinette.chatre@...el.com>
> ---

Reinette