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SubjectRe: [PATCH] x86: mtrr cleanup for converting continuous to discrete - auto detect v2
On Thu, May 1, 2008 at 2:33 PM, H. Peter Anvin <> wrote:
> Yinghai Lu wrote:
> >
> > > Overall, I'm feeling there is something really completely wrong if this
> > > needs manual tunables of any sort.
> > >
> >
> > the problem is BIOS set MTRR like BIG WB - SOME SAMLL UC to spare mtrr
> regs.
> >
> > but later X server driver want to set some range to WC. that already
> > is fallen in UC...
> >
> That's not the point. I understand you want to flatten the layout. The
> point is: why do you need manual tunables for the algorithm to do the right
> thing?

optimal result is not losing covering for ranges that is originally
covered, and still keep as many of spare mtrr entries for X server
we only have 8 mtrrs, could lose some covering because of run out of mtrr regs.
So we need to search it according to chunk/gran with ram ranges that
is defined by old mtrr layout.

and if we can not find the optimal setting, user could select one
setting (chunk/gran size) to boot next time, but he will lose some
for some regions. later trim_mtrr will remove those range from e820 map


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