Re: [PATCH v2] cxl/region: Create node access attributes for CFMWS-only NUMA nodes

[Alison Schofield <alison.schofield@intel.com>]

On Thu, Sep 17, 2026 at 10:46:32AM +0800, Guixin Liu wrote:
> A NUMA node that only backs a CXL fixed memory window and is not
> enumerated by SRAT has no memory_target in the HMAT code, so
> hmat_callback() exits early at find_mem_target() and never creates
> the node's accessN attributes:
> /sys/devices/system/node/nodeX/accessN/initiators/* stays missing.
> 
> Commit debdce20c4f2 ("cxl/region: Deal with numa nodes not enumerated
> by SRAT") had the CXL region notifier call node_set_perf_attrs()
> directly for such nodes, but commit 2e454fb8056d ("cxl, acpi/hmat:
> Update CXL access coordinates directly instead of through HMAT")
> replaced it with node_update_perf_attrs(), which only updates
> attributes that already exist and thus does nothing for these nodes.
> 
> Create the attributes with node_set_perf_attrs() when the node is not
> backed by a real SRAT pxm.
> 
> Tested on a QEMU CXL topology with a CFMWS window not described by
> SRAT or HMAT: node1/access0/initiators/{read,write}_{bandwidth,latency}
> appear with the calculated coordinates once the region's first memory
> block comes online.

Reviewed-by: Alison Schofield <alison.schofield@intel.com>