Messages in this thread | | | Date | Sat, 04 Oct 2008 18:52:45 -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: >> 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. > > so it is safe to put it in WB, and can be spare some regs because it > start from base 0.
Yes, my point was that you can make those whatever you want. It doesn't have to be WB; it can be any value.
>> 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. > > EFI will not use fixed-mtrr for first 1M? and not cover first 1M in > var mtrr with WB? that will run out mtrr regs..
There are some systems which, apparently, don't have RAM there. Don't ask me how or why.
-hpa
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