iommu: Allow selecting page sizes per domain

iommu: Allow selecting page sizes per domain

Many IOMMUs support multiple page table formats, meaning that any given
domain may only support a subset of the hardware page sizes presented in
iommu_ops->pgsize_bitmap. There are also certain use-cases where the
creator of a domain may want to control which page sizes are used, for
example to force the use of hugepage mappings to reduce pagetable walk
depth.

To this end, add a per-domain pgsize_bitmap to represent the subset of
page sizes actually in use, to make it possible for domains with
different requirements to coexist.

Signed-off-by: Will Deacon <[email protected]>
[rm: hijacked and rebased original patch with new commit message]
Signed-off-by: Robin Murphy <[email protected]>
Acked-by: Will Deacon <[email protected]>
Signed-off-by: Joerg Roedel <[email protected]>