Public bug reported:

The DPA region needs VFIO_REGION_INFO_FLAG_MMAP so a VMM can mmap it and
map it into stage-2 for the device to reach over ATS. Without the flag
the VMM keeps DPA as a slow-path I/O region that the stage-2 listener
skips, and the GPU's ATS access to DPA-resident memory never resolves.

The dpa_mmap_fault selftest is skipped when the flag is absent. With the
flag set it runs, but its raw host CPU load/store of DPA does not model
how a VMM uses the region: the VMM mmaps DPA and maps it into the IOAS,
and the guest reaches it through stage-2. Rewrite the test to do the
same (mmap plus iommu_map) and drop the host dereference.

** Affects: linux-nvidia-bos (Ubuntu)
     Importance: Undecided
         Status: New

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https://bugs.launchpad.net/bugs/2160591

Title:
  vfio/cxl: Advertise DPA mmap and update its selftest

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