Handle writethrough mappings (as opposed to writeback) better: - a writeback->writethrough downgrade only requires a cache writeback, not a   writeback and invalidate. - apparently the 88200 does not behave correctly (i.e. according to its   documentation) when a given page is accessed with both writethrough and   writeback cacheability (even though the cache lines are physically indexed   and physically tagged), so make sure to force writeback of writeback pages   when they risk being reused as writethrough (hair_count -= MAXHAIR).
Handle writethrough mappings (as opposed to writeback) better:
- a writeback->writethrough downgrade only requires a cache writeback, not a
  writeback and invalidate.
- apparently the 88200 does not behave correctly (i.e. according to its
  documentation) when a given page is accessed with both writethrough and
  writeback cacheability (even though the cache lines are physically indexed
  and physically tagged), so make sure to force writeback of writeback pages
  when they risk being reused as writethrough (hair_count -= MAXHAIR).

Better coherency in page table backing store cacheability: these need to be
cache invalidated on 88100+88200 (because of hardware update of modified and
used pte bits), and writethrough on 88110.

orumin/openbsd-efivars,orumin/openbsd-efivars,orumin/openbsd-efivars,orumin/openbsd-efivars