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

["H. Peter Anvin" <hpa@zytor.com>]

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