Re: [PATCH 1/2] x86/resctrl: Add io_alloc_min_cbm_all interface for CBM reset

[Aaron Tomlin]

On Tue, Nov 11, 2025 at 01:40:45AM +0000, Luck, Tony wrote:
> > Seems like user space has needed information to perform a sane reset?
> 
> Like this:
> 
> 1) 	Read info files to figure out what minimum mask is needed for this system
> 2)	Use Babu's suggested syntax of
> 		# echo "L3:*={min_mask_from_step_1}" > schemata
> 
> Rather than Aaron's
> 
> 	# echo "L3:*=0" > schemata

Hi Tony,

I am satisfied with either approach.

However, to clarify, the primary function of the "io_alloc_min_cbm_all"
interface is to efficiently set the lowest architecturally valid CBM across
all shared L3 domains. This operation relies entirely on
r->cache.min_cbm_bits. Since this value is guaranteed by the hardware to be
valid, this approach is robust and will not return an error (e.g., -EINVAL)
to userspace.


Kind regards,
-- 
Aaron Tomlin