Re: [PATCH] ACPI: NUMA: Only parse CFMWS at boot when CXL_ACPI is on

[Gregory Price]

On Thu, Mar 05, 2026 at 10:33:42AM +1300, Kai Huang wrote:
> Increasing the 'nr_node_ids' has side effects.  For instance, it is
> widely used by the kernel for "highest possible NUMA node" based memory
> allocations.  It also impacts userspace ABIs, e.g., some NUMA memory
> related system calls such as 'get_mempolicy' which requires 'maxnode'
> not being smaller than the 'nr_node_ids'.
> 

Is this a Linux issue or a Firmware issue?

Is GNR exporting more CFMWS than it should?

Is your SRAT missing entries for CFMWS that are otherwise present?

Are the CFMWS empty? (is that even valid)

> E.g., on the aforementioned GNR platform, the "Slab" in /proc/meminfo is
> reduced with this change (when CXL_ACPI is off):
> 
> 	w/ this change		w/o
> 
> Slab	900488 kB		923660 kB
> 

This is a good effect, but I still question the premise.

We don't usually want #ifdef's inside of .c files if we can avoid it.

~Gregory