Merge branch 'nesting_reserved_regions' into iommufd.git for-next

Merge branch 'nesting_reserved_regions' into iommufd.git for-next

Nicolin Chen says:

=========
IOMMU_RESV_SW_MSI is a unique region defined by an IOMMU driver. Though it
is eventually used by a device for address translation to an MSI location
(including nested cases), practically it is a universal region across all
domains allocated for the IOMMU that defines it.

Currently IOMMUFD core fetches and reserves the region during an attach to
an hwpt_paging. It works with a hwpt_paging-only case, but might not work
with a nested case where a device could directly attach to a hwpt_nested,
bypassing the hwpt_paging attachment.

Move the enforcement forward, to the hwpt_paging allocation function. Then
clean up all the SW_MSI related things in the attach/replace routine.
=========

Based on v6.11-rc5 for dependencies.

* nesting_reserved_regions: (562 commits)
  iommufd/device: Enforce reserved IOVA also when attached to hwpt_nested
  Linux 6.11-rc5
  ...