Re: [PATCH] cxl/region: Delay inserting iomem resource until auto region commit

[Gregory Price <gourry@gourry.net>]

On Wed, Feb 11, 2026 at 10:22:46PM -0800, Alison Schofield wrote:
> During auto region assembly the region driver inserts the region
> resource into the iomem tree when the first endpoint arrives and
> region assembly begins. If the region later fails to assemble, the
> resource can remain stranded in the iomem tree, making it appear like
> a DAX region is a child of the CXL region, when that is not true.
> 
> For example:
> 68e80000000-8d37fffffff : CXL Window 9
>   68e80000000-70e7fffffff : Soft Reserved
>     68e80000000-70e7fffffff : region9
>       68e80000000-70e7fffffff : dax19.0
>         68e80000000-70e7fffffff : System RAM (kmem)
> 
> In the above case, region9 failed to assemble, yet proc/iomem shows
> the DAX region as being parented under a CXL region. In reality, the
> CXL region is in a disabled state and the DAX region is managed by the
> HMEM driver.
> 
> Examining /proc/iomem is one way users inspect the memory topology,
> and with this patch that view remains accurate.
> 
> Delay insertion of the iomem resource until the auto region reaches
> the commit state. Introduce the res_want_insert field to track whether
> the region's resource should be inserted into the iomem tree.
> 

Can you show the before/after of the iomap failure case just to make it
explicit what the user sees before / after?  I think I understand, but
worth just having the explicit data for the failure case in the
changelog.

Thanks!
~Gregory