UMA_MD_SMALL_ALLOC

[Nathan Whitehorn]

In doing the G5 port, I have a problem with the UMA_MD_SMALL_ALLOC 
option. Because the G5 does not have BAT, this is broken. Even if we 
were to emulate it with pages, this is not a useful thing to have, since 
the point of the option would be defeated. But removing it would 
pessimize the G3/G4 port (the AIM code also panics late in boot without 
it, but that is a separate issue).

There doesn't seem to be a way to twiddle it at runtime, which is a 
major problem if we want to have a single kernel running on all OEA 
machines. So I'm not sure what to do. Thoughts?

Also, an update on the G5 port: the PMAP stuff is done to the point 
where the kernel boots all the way to panicing about not having a PIC, 
which is late in the boot process and implies that only device support 
remains. Trap handling is up and running as well. And (with the 
exception of UMA_MD_SMALL_ALLOC) the same kernel also boots on my G3.
-Nathan