Re: [RFC Patch] use MTRR for write combining if PAT is notavailable

[Suresh Siddha]

On Mon, 2009-10-19 at 08:31 -0700, Ingo Molnar wrote:
> * Thomas Schlichter <thomas.schlichter@xxxxxx> 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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