This is considered experimental, with no guarantee of backwards
compatibility, Userspace built with a 4k PAGE_SIZE assumption will
likely try to pass in a too small size when working with APIs that
take a multiple of a page, e.g. mmap. Userspace built with a 16k
PAGE_SIZE assumption is more likely to run on a kernel providing
4k pages, however the best option is to not use a hard coded value
and ask for it when needed.
This is ready for testing, however some drivers may fail as they
make assumptions that PAGE_SIZE is 4k. Many issues have been found,
however more work is needed to test more hardware.