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    SubjectRe: [PATCH 2/3] x86: mtrr_cleanup: first 1M should be coverred in var mtrrs
    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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