Ok...

Here's where I am so far:

	* Have integrated a bunch of suggestions from Chris Demetriou.
	  (THANKS VERY MUCH, Chris, for you extremely helpful input!)

	* Works on R3000 (DECstation 5000/200)

	* Works on R4400 w/ no L2 cache[*] (NEC Image RISCstation)

	* Does not work on RM52xx (Algorithmics P-5064)

	* Have not yet tested R4600 (SGI Indy).  I want to get the
	  RM52xx working, first, since the R4600 cache is "like" the
	  RM52xx cache, except with hardware bugs :-)

Considering that it works on the R4400 (direct-mapped cache) and not
the RM52xx (2-way set-associative), I probably have a bug in the 2-way
cache handling code.

[*] Actually, the NEC Image does have an L2 cache, but it's not like
a normal R4000-class L2 cache -- it's a 128K snooping cache implemented
in the memory system, and is not something the kernel mucks with.  For
our purposes, this is "no L2 cache".  Someone with an R4400 DECstation
5000/260 is going to test for me, and that should exercise the R4000-class
L2 cache case.

Anyone with a TX39xx-based machine, I would appreciate it if you would
send me a kernel configuration file, so I can build a kernel for you
to test.

-- 
        -- Jason R. Thorpe <thorpej@zembu.com>