linux-kernel - Re: [PATCH 1/4] Documentation: x86: Contiguous cbm isn't all X86

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Date:   Fri, 7 Jun 2019 14:24:20 -0700
From:   Fenghua Yu <fenghua.yu@...el.com>
To:     James Morse <james.morse@....com>
Cc:     linux-doc@...r.kernel.org, x86@...nel.org,
        Jonathan Corbet <corbet@....net>,
        Reinette Chatre <reinette.chatre@...el.com>,
        Babu Moger <Babu.Moger@....com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/4] Documentation: x86: Contiguous cbm isn't all X86

On Fri, Jun 07, 2019 at 04:14:06PM +0100, James Morse wrote:
> Since commit 4d05bf71f157 ("x86/resctrl: Introduce AMD QOS feature")
> resctrl has supported non-contiguous cache bit masks. The interface
> for this is currently try-it-and-see.
> 
> Update the documentation to say Intel CPUs have this requirement,
> instead of X86.
> 
> Cc: Babu Moger <Babu.Moger@....com>
> Signed-off-by: James Morse <james.morse@....com>
> ---
>  Documentation/x86/resctrl_ui.rst | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/Documentation/x86/resctrl_ui.rst b/Documentation/x86/resctrl_ui.rst
> index 225cfd4daaee..066f94e53418 100644
> --- a/Documentation/x86/resctrl_ui.rst
> +++ b/Documentation/x86/resctrl_ui.rst
> @@ -342,7 +342,7 @@ For cache resources we describe the portion of the cache that is available
>  for allocation using a bitmask. The maximum value of the mask is defined
>  by each cpu model (and may be different for different cache levels). It
>  is found using CPUID, but is also provided in the "info" directory of
> -the resctrl file system in "info/{resource}/cbm_mask". X86 hardware
> +the resctrl file system in "info/{resource}/cbm_mask". Intel hardware
>  requires that these masks have all the '1' bits in a contiguous block. So
>  0x3, 0x6 and 0xC are legal 4-bit masks with two bits set, but 0x5, 0x9
>  and 0xA are not.  On a system with a 20-bit mask each bit represents 5%
> -- 
> 2.20.1
>
 
Acked-by: Fenghua Yu <fenghua.yu@...el.com>

Thanks.

-Fenghua Yu