Re: Current kernel with http://gnats.netbsd.org/39965 and pmap patches

[Izumi Tsutsui <tsutsui%ceres.dti.ne.jp@localhost>]

tjamaloo%gmail.com@localhost wrote:

> Thanks for the patch. I applied it and tested with 030, but unfortunately 
> kernel
> panics right after it has loaded installer to ram disk with:

Ok, I was actually confused.
Now I think current Sysptmap code is correct.

- 4KB/page systems require 4MB address space for page tables
  to handle whole 4GB address space.

- 8KB/page systems require 2MB PT pages to handle 4GB range.

- Sysptmap should be mapped as a part of Sysmap in pmap code.

  - On 4KB page systems, Sysmap is allocated at 0xffc00000
    and its range is from 0xffc00000 to 0xffffffff,
    so Sysptmap_pa should be mapped at the end of KVA.

  - On 8KB/page systems, Sysmap is allocated at
    0xff000000 (-PAGE_SIZE * NPTEPG) so its range is from
    0xff000000 to 0xff1fffff, i.e. there is some unused region.
    This means Sysptmap_pa should be registered in
    the PTE entry at &((pt_entry_t *)Sysptmap)[256 - 1],
    not at [NPTEPG - 1] which 4KB/page systems use.

Maybe we should replace some NPTEPG macro (that is actually TIB_SIZE)
with TIA_SIZE, which the "256" means.

Anyway, I'll try to see if there is more possible pitfall
for 8KB page systems in m68k pmap code...
---
Izumi Tsutsui