Messages in this thread | | | Date | Sat, 04 Oct 2008 17:46:24 -0700 | From | "H. Peter Anvin" <> | Subject | Re: [PATCH 2/3] x86: mtrr_cleanup: first 1M should be coverred in var mtrrs |
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Yinghai Lu wrote: > + /* > + * [0, 1M) should always be coverred by var mtrr with WB > + * and fixed mtrrs should take effective before var mtrr for it > + */ > + nr_range = add_range_with_merge(range, nr_range, 0, > + (1ULL<<(20 - PAGE_SHIFT)) - 1); > + /* sort the ranges */ > + sort(range, nr_range, sizeof(struct res_range), cmp_range, NULL); > +
The first 1 MB is a total don't care for the variable MTRRs -- they don't have to be covered *or* uncovered, since the entire first 1 MB is addressed by fixed MTRRs.
In practice, it is *likely* that you're going to want to merge it with a WB MTRR, but with various vendors doing all kinds of strange things on EFI-damaged platforms, it may not always be that way.
-hpa
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