Re: [PATCH] resource: fix false warning in __request_region()

[Akinobu Mita]

2025年7月20日(日) 8:31 Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>:
>
> On Sat, 19 Jul 2025 20:26:04 +0900 Akinobu Mita <akinobu.mita@xxxxxxxxx> wrote:
>
> > A warning is raised when __request_region() detects a conflict with a
> > resource whose resource.desc is IORES_DESC_DEVICE_PRIVATE_MEMORY.
> >
> > But this warning is only valid for iomem_resources.
> > The hmem device resource uses resource.desc as the numa node id, which can
> > cause spurious warnings.
> >
> > This change fixes this by restricting the warning to only iomem_resource.
> > This also adds a missing new line to the warning message.
>
> What are the circumstance which cause this warning?  Are real world
> users hitting this?  If so, should we backport this fix into earlier
> kernels?

This warning actually appeared on a machine with multiple cxl memory expanders.
One of the NUMA node id is 6, which is the same as the value of
IORES_DESC_DEVICE_PRIVATE_MEMORY.

In this environment it was just a spurious warning, but when I saw the warning
I suspected a real problem so it's better to fix it.

Fixes: b926b7f3baec ("mm/resource: Move HMM pr_debug() deeper into
resource code")