Hi Andi,

Just looking at your 4 level page tables patch, I wondered why the extra
level isn't inserted between pgd and pmd, as that would appear to be the
least intrusive (conceptually, in the generic code). Also it maybe matches
more closely the way that the 2->3 level conversion was done.

I've been toying with it a little bit. It is mainly just starting with
your code and doing straight conversions, although I also attempted to
implement a better compatibility layer that does the pagetable "folding"
for you if you don't need to use the full range of them.

Caveats are that there is still something slightly broken with it on i386,
and so I haven't looked at x86-64 yet. I don't see why this wouldn't work
though.

I've called the new level 'pud'. u for upper or something.

Sorry the patch isn't in very good shape at the moment - I won't have time
to work on it for a week, so I thought this would be a good point just to
solicit initial comments.

Patches against recent -bk. patch 1/4 attached.

Thanks,
Nick