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

[Fenghua Yu]

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@xxxxxxx>
> Signed-off-by: James Morse <james.morse@xxxxxxx>
> ---
>  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@xxxxxxxxx>

Thanks.

-Fenghua Yu