64-bit paddr_t and mmap()?

I'm trying to mmap a framebuffer device under evbmips, using a 64-bit
paddr_t.   (Alchemy PCI space is located in the upper portion of the
36-bit MIPS physical address space.)

Anyway, the mmap works fine.  I'm able to draw a picture on screen.

But when the application exits (and hence does an implicit munmap()), I
get a panic in pmap_remove_pv, called from pmap_remove, where it looks
like a NULL "pg" pointer is being passed.

I'm curious if anyone else has used 64-bit paddr_t's and mmap(), e.g. on
ARC.  I'm wondering if maybe I'm trying to do something new, or if there
is some known fault, or if it is known to work on other platforms.  Any
info that might help me restrict where I am looking would be useful to
me.  :-)

-- 
Garrett D'Amore, Principal Software Engineer
Tadpole Computer / Computing Technologies Division,
General Dynamics C4 Systems
http://www.tadpolecomputer.com/
Phone: 951 325-2134  Fax: 951 325-2191