Re: [RFC Patch] use MTRR for write combining if PAT is not available

[Thomas Schlichter]

Suresh Siddha wrote:
> I think we can simplify this  by just using mtrr_add_page() and avoid
> all the complexity that comes with mtrr_add_unaligned().
> 
> pci_mmap_range() should call one mtrr_add_page() if the base and size
> are nicely aligned. Almost all the cases, this is the usage sequence
> here anyway.

Ingo Molnar wrote:
> Can we eliminate mtrr_add_unaligned() as Suresh suggested, and still 
> make it work on your testbox?

Yes, I had that in the first place, but Jan suggested to extend it to also
handle non-aligned, non-power-of-two cases:
  http://marc.info/?l=linux-kernel&m=125541951529918&w=2

So if it's OK for Jan, I'll reduce the functionality again and use mtrr_add()
instead. Btw. this simply means to drop mtrr_add_unaligned(), all the other
parts are still required for reference counting and a proper mtrr_del() on file
close.

Kind regards,
  Thomas
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