Re: question about MTRR areas on x86_64

[Eric W. Biederman]

Andi Kleen <ak@xxxxxx> writes:

> Markus Lidel <Markus.Lidel@xxxxxxxxxxxxxxxxx> writes:
> >
> > Could it be because the machine has too much memory, or is there a bug in the
> I2O driver?
> 
> 
> The problem comes from the BIOS who set up reg00 to be overlapping
> over other areas. The Linux MTRR driver cannot deal with overlapping
> MTRRs, in fact it is sometimes impossible because it could run
> out of registers or violate some of the MTRR restrictions.

And the BIOS is using overlapping MTRRs because otherwise it would run
out.
 
> It's a long standing problem, eventual fix will be to get rid
> of MTRRs completely and only use PAT. But it needs a bit more work.


That would be nice to see.

Eric
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