Re: [PATCH v13 03/25] x86/resctrl: Check if monitoring features are supported

[Reinette Chatre]

Hi Tony,

On 9/28/26 3:14 PM, Tony Luck wrote:
> Both Intel and AMD manuals say that software must first check
> CPUID(0x7,0x0).EBX[12] to see if any monitoring features are supported before
> checking for resource specific features supported in subleaves.
> 
> Each of the L3 monitoring features is further gated by CPUID(0xF,0x0).EDX[1].
> 
> Add checks for these feature bits.
> 
> Maintainer note: No need to backport this fix. No issues have been seen
> from this failure to follow the exact enumeration process in the manual.
> 
> Fixes: cbc82b172638 ("x86: Add support for Intel Cache QoS Monitoring (CQM) detection")
> Signed-off-by: Tony Luck <tony.luck@xxxxxxxxx>
> ---
> v13:

v12 feedback at https://lore.kernel.org/lkml/430f74d4-5d04-4f95-b7e9-83dcd5cd5ba5@xxxxxxxxx/

> 	Dropped (Linux: X86_FEATURE_*) from commit comment

My comment was only about the "Linux:" caveat, ideally applied to previous patch also.
The feature flags are useful.

> 	s/specific features/resource specific features/

Suggestion was "resource specific monitoring features" to emphasize connection with 
"monitoring features" that precedes it.

> 	s/L3-based monitoring features/L3 monitoring features/

Suggestion was "L3 resource monitoring features" with intention to connect
it to first paragraph usage of resource. 

> 	Added maintainer note about not back porting.

Maintainer notes are not intended to be included during merge and should thus
be below the "---".

I did give preliminary Reviewed-by tag in previous version. Giving it again should not
be necessary since I am just repeating myself here.

Reinette