linux-kernel - Re: [PATCH v2 1/1] mm: numa_memblks: Identify the accurate NUMA ID of CFMW

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Message-ID: <aXOl9CN_66HywIjZ@gourry-fedora-PF4VCD3F>
Date: Fri, 23 Jan 2026 11:46:44 -0500
From: Gregory Price <gourry@...rry.net>
To: Cui Chao <cuichao1753@...tium.com.cn>
Cc: dan.j.williams@...el.com, Andrew Morton <akpm@...ux-foundation.org>,
	Jonathan Cameron <Jonathan.Cameron@...wei.com>,
	Mike Rapoport <rppt@...nel.org>,
	Wang Yinfeng <wangyinfeng@...tium.com.cn>,
	linux-cxl@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org
Subject: Re: [PATCH v2 1/1] mm: numa_memblks: Identify the accurate NUMA ID
 of CFMW

On Thu, Jan 22, 2026 at 04:03:49PM +0800, Cui Chao wrote:
> 2.Why a Kernel Update is Recommended Over a Firmware Update:
> 
> In the scenario of dynamic CXL region creation, the association between the
> memory's HPA range and its corresponding NUMA node is established when the
> kernel driver performs the commit operation. This is a runtime, OS-managed
> operation where the platform firmware cannot intervene to provide a fix.
>

This is not accurate

The memory-to-node association for CXL memory is built by acpi logic:

   linux/drivers/acpi/numa/srat.c

Specifically:

   acpi_parse_memory_affinity()  /* if SRAT entry exists */
      -> numa_add_memblk(node, start, end)

   acpi_parse_cfmws()  /* if no SRAT entry exists */
      -> numa_add_reserved_memblk(node, start, end)


This patch implies the latter is occurring - as it queries the reserved
block associations - meaning your platform is not shipping SRAT tables
for CXL memory regions.

We have only seen this in QEMU - and this is correctable in firmware.

But if this is shipped hardware, letting us know the platform lets us
know whether we should backport it.

---

All that said, this does look harmless, and seems reasonable - but the
changelog should reflect what the hardware is doing above.

~Gregory