[ ... continue on TLB issue ... ]

> I found several drawbacks in the MD portion of NetBSD/mips VM.

'TLBmod' exception posted when absense of D bit means, 'detected the
necessity of TLB entry modification if the page is to be useful'.  The
D bit is not simply for 'detected voliation of access protection',
'detected COW condition on the page', 'detected deferred page content
modification or value (re)fill', nor 'this page was formerly clean but
to be written or to be purged out to 2ndary storage'.  Wow... 

Tohru Nishimura