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SubjectRe: [RFC Patch] use MTRR for write combining if PAT is not available
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On Mon, 2009-10-19 at 08:31 -0700, Ingo Molnar wrote:
> * Thomas Schlichter <thomas.schlichter@web.de> wrote:
>
> > I don't think this is a good idea, Robert Hancock wrote there may be
> > millions of such Laptops (Core Solo/Duo erratum AE7, Pentium M erratum
> > Y31) :
> >
> > http://marc.info/?l=linux-kernel&m=125537136105246&w=2
> >
> > > or Perhaps just try to add mtrr only for the pci mmap case like the
> > > 4th patch in this series..
> >
> > I'd prefer this! ;-)
>
> Hm, we could perhaps do that - but i think we should only do that on
> systems that have PAT disabled.
>
> Which brings up the question of how to properly QA such a narrow segment
> of the market. Maybe disabling CONFIG_X86_PAT should enable that logic
> too.

Also, I think we can simplify and avoid mtrr_add_unaligned() and worry
only about the pci mmap aligned cases etc. Those are the only
interesting ones.

thanks,
suresh



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