Re: [RFC PATCH 1/4] cxl/extent: Promote cxlr_dax->region_extent to an xarray

[Jonathan Cameron]

> Look at the diagrams in this presentation:
> 
> https://lpc.events/event/18/contributions/1826/attachments/1435/3335/LPC2024_CXL_DCD-v2.pdf
> 
> 'DAX dev 1' covers memory from Extent A and Extent B.  What yall will want
> to do is ensure that the region extents which get surfaced are ordered
> based on the sequence number _when_ _the_ _dax_ _device_ is created.  The
> order they come into the host does not really matter.  Although yea the
> spec has a bunch of rules...  so whatever, follow those.  But it is the
> dax device which groups the extents into a contiguous HPA range and maps

On this bit, HPA?  Why would extents be contiguous in HPA?  Contiguous
in the DAX device mapping sure, but not HPA.

> those ranges through struct dev_dax->ranges.