603 support

[Benjamin Herrenschmidt]

>
>As a side note, I think a private TLB might be a good thing
>on SMP systems too in order to sidestep locking issues,
>at least as a short term solution. 

Well, SMP locking issues aren't that bad actually. I never
found the time to go deep enough in my understanding of MOL low
level MMU stuff, but it should only be a matter of taking the
hash table lock when accessing the hash table or issuing tlbie's,
though I'm not sure what MOL does regarding linux PTEs (do you
touch them at all ?). The VM somewhat relies on us properly
setting PAGE_ACCESSED when putting things in the hash table on
fault, and PAGE_HASHPTE should be set for a page that may be
in the hash or the kernel flush code would fail to flush the
page, but I beleive you have already that working.

>> At any rate, I'll see what I can do to improve things.
>
>It should be relatively easy to debug the current code.
>If you insert a couple of 
>
>	DEBUGGER(num) / DEBUGGER_SAVE(num)
>
>statements in the exception handlers and fire up mol in
>debugger mode, you should be able to see what is going on. 
>(It is safe to use these statements almost anywhere.)
>
>Cheers,