How FreeBSD manage more than 4GB on 32 bits architecture

[Adrian Chadd]

Hi!

This sounds... very exciting. I'd start by taking a look at how PAE
works - you may be able to reuse all those pieces and just implement
more than the 4 bits of physical address space. The interesting bits
of PAE aren't just the extension of the physical addresses, but all
the management of mapping things into virtual address space as
required.

I haven't looked at the MIPS side of things though. IIRC, on MIPS32 we
only implement up to what the direct map KSEG supports, so a little
PAE ish work would be required there to make things work right.

So, I'd start by looking at how PAE on i386 works. I think there's a
little bit of KVA exhaustion going on in -HEAD with i386 PAE that can
be fixed with a little bit of attention. The rest of the basic PAE
stuff should still work fine. Then if you need it for MIPS, you'll
need to sketch out how you expect PAE to work on MIPS, and then make
up a project for that. :)



-adrian