linux-kernel - Re: [PATCH v2 07/33] x86/intel_rdt: Add support for Cache Allocation detection

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Date:   Thu, 8 Sep 2016 13:50:23 +0200
From:   Borislav Petkov <bp@...e.de>
To:     Fenghua Yu <fenghua.yu@...el.com>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        "H. Peter Anvin" <h.peter.anvin@...el.com>,
        Ingo Molnar <mingo@...e.hu>, Tony Luck <tony.luck@...el.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Tejun Heo <tj@...nel.org>,
        Stephane Eranian <eranian@...gle.com>,
        Marcelo Tosatti <mtosatti@...hat.com>,
        David Carrillo-Cisneros <davidcc@...gle.com>,
        Shaohua Li <shli@...com>,
        Ravi V Shankar <ravi.v.shankar@...el.com>,
        Vikas Shivappa <vikas.shivappa@...ux.intel.com>,
        Sai Prakhya <sai.praneeth.prakhya@...el.com>,
        linux-kernel <linux-kernel@...r.kernel.org>, x86 <x86@...nel.org>
Subject: Re: [PATCH v2 07/33] x86/intel_rdt: Add support for Cache Allocation
 detection

On Thu, Sep 08, 2016 at 02:57:01AM -0700, Fenghua Yu wrote:
> From: Vikas Shivappa <vikas.shivappa@...ux.intel.com>
> 
> This patch includes CPUID enumeration routines for Cache allocation and
> new values to track resources to the cpuinfo_x86 structure.
> 
> Cache allocation provides a way for the Software (OS/VMM) to restrict
> cache allocation to a defined 'subset' of cache which may be overlapping
> with other 'subsets'. This feature is used when allocating a line in
> cache ie when pulling new data into the cache. The programming of the
> hardware is done via programming MSRs (model specific registers).
> 
> Signed-off-by: Vikas Shivappa <vikas.shivappa@...ux.intel.com>
> Signed-off-by: Fenghua Yu <fenghua.yu@...el.com>
> Reviewed-by: Tony Luck <tony.luck@...el.com>
> ---

...

> diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h
> index 92a8308..62d979b9 100644
> --- a/arch/x86/include/asm/cpufeatures.h
> +++ b/arch/x86/include/asm/cpufeatures.h
> @@ -12,7 +12,7 @@
>  /*
>   * Defines x86 CPU feature bits
>   */
> -#define NCAPINTS	18	/* N 32-bit words worth of info */
> +#define NCAPINTS	19	/* N 32-bit words worth of info */
>  #define NBUGINTS	1	/* N 32-bit bug flags */
>  
>  /*
> @@ -220,6 +220,7 @@
>  #define X86_FEATURE_RTM		( 9*32+11) /* Restricted Transactional Memory */
>  #define X86_FEATURE_CQM		( 9*32+12) /* Cache QoS Monitoring */
>  #define X86_FEATURE_MPX		( 9*32+14) /* Memory Protection Extension */
> +#define X86_FEATURE_RDT		( 9*32+15) /* Resource Director Technology */
>  #define X86_FEATURE_AVX512F	( 9*32+16) /* AVX-512 Foundation */
>  #define X86_FEATURE_AVX512DQ	( 9*32+17) /* AVX-512 DQ (Double/Quad granular) Instructions */
>  #define X86_FEATURE_RDSEED	( 9*32+18) /* The RDSEED instruction */
> @@ -286,6 +287,9 @@
>  #define X86_FEATURE_SUCCOR	(17*32+1) /* Uncorrectable error containment and recovery */
>  #define X86_FEATURE_SMCA	(17*32+3) /* Scalable MCA */
>  
> +/* Intel-defined CPU features, CPUID level 0x00000010:0 (ebx), word 18 */

Seems like this leaf is dedicated to CAT and has only 2 feature bits
defined in the SDM. Please use init_scattered_cpuid_features() instead
of adding a whole CAP word.

-- 
Regards/Gruss,
    Boris.

SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg)
--