linux-kernel - Re: [PATCH v7 01/10] x86/cpufeatures: Add support for L3 Smart Data Cache Injection Allocation Enforcement

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Message-ID: <20250710232607.GEaHBMD54IXx3e8UpH@fat_crate.local>
Date: Fri, 11 Jul 2025 01:26:07 +0200
From: Borislav Petkov <bp@...en8.de>
To: Babu Moger <babu.moger@....com>
Cc: corbet@....net, tony.luck@...el.com, reinette.chatre@...el.com,
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Subject: Re: [PATCH v7 01/10] x86/cpufeatures: Add support for L3 Smart Data
 Cache Injection Allocation Enforcement

On Thu, Jul 10, 2025 at 12:16:15PM -0500, 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 feature details are documented 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>
> ---
> v7: No changes. Fixed few conflicts in
>    arch/x86/include/asm/cpufeatures.h
>    arch/x86/kernel/cpu/scattered.c
> 
> v6: Resolved conflicts in cpufeatures.h.
> 
> v5: No changes.
> 
> v4: Resolved a minor conflict in cpufeatures.h.
> 
> v3: No changes.
> 
> v2: Added dependancy on X86_FEATURE_CAT_L3
>     Removed the "" in CPU feature definition.
>     Minor text changes.
> ---
>  arch/x86/include/asm/cpufeatures.h | 1 +
>  arch/x86/kernel/cpu/cpuid-deps.c   | 1 +
>  arch/x86/kernel/cpu/scattered.c    | 1 +
>  3 files changed, 3 insertions(+)

Acked-by: Borislav Petkov (AMD) <bp@...en8.de>

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette