Linus Torvalds wrote:

> Nick, can you see if such a patch is possible? I'll test ppc64 still 
> working..
> 

OK I seem to have got something working after fumbling around in the
dark for a bit. I apologise if it blows up straight away for you, which
isn't unlikely.

Tested only on i386 2-levels for now (not much point in testing i386
3 levels really). I'll do some testing on ia64 and x86-64 tomorrow, but
I've run out of time tonight.

You'll want the full rollup here (against 2.6.10-rc3):
http://www.kerneltrap.org/~npiggin/vm/4level.patch.gz

And attached is the broken out patch (included in the above). An arch
only needs to include this in asm/pgtable.h, and no other changes. As
you see it wasn't _quite_ as clean as Hugh had hoped, but not too bad.

Nick