As long as I know there is no finished code to support 64bit address
range.  All we have is to handle original 32bit MIPS address space
arrangement.  L4-mips can provide you some clue, however, it's a
single 64bit address space OS dissimilar to any UNIX-like process
model.

I have my own idea to have 64bit pmap whose foundation stands at
inverse PTE lookup similar to PPC implementation.  I have never
materialized any line of code.

Toru Nishimura/ALKYL Technology