I thought I posted the following mail, but it seems this mail 
may be lost in somewhere..

From: Noriyuki Soda <soda@sra.co.jp>
> I'd like to change paddr_t from 32bit to 64bit on arc port before
> NetBSD-1.5 branch cut by introducing symbol "_MIPS_PADDR_T_64BIT" in
> <machine/types.h>.

I forgot to mention the following:

- the intention of this patch is to support 64bit device address
  space of arc port. framebuffer address and PCI bus space address of
  some platforms locate beyond 4GB (32bit address) boundary.

- fortunately, userland binary compatibility (esp. about kvm
  utilities) will not be lost by this patch, since current in-tree
  kvm utilities seem not to refer structures which have paddr_t
  members.
--
soda