Messages in this thread | | | Date | Fri, 28 Sep 2012 20:16:30 -0700 | From | "H. Peter Anvin" <> | Subject | Re: [RFC] x86: mtrr: Constrain WB MTRR to max phys mem prior to cleanup |
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On 09/28/2012 10:37 AM, Peter Hurley wrote: > > An interesting side note: more recent revisions of this BIOS (rev. A11) > report one less variable MTRR (so, IA32_MTRRCAP is writable?) > >>> However, the right way to fix that is to use the PAT interfaces, which >>> doesn't have this drawback -- then MTRR cleanup becomes entirely >>> superfluous and the problem goes away. >> Do you mean disable MTRR totally here? > > Well, since PAT entries marked WC override all MTRR settings, whatever > the BIOS set the variable MTRRs to becomes irrelevant, so not disabled > but rather ignored. >
The whole point is that the display stuff should not use MTRR, but rather use PAT to provide WC. Then we don't need to "clean up" the BIOS-set MTRRs.
-hpa
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