Messages in this thread | | | Date | Tue, 12 May 2015 18:31:48 +0200 | From | Borislav Petkov <> | Subject | Re: [PATCH v4 7/7] mtrr, mm, x86: Enhance MTRR checks for KVA huge page mapping |
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On Tue, May 12, 2015 at 08:30:30AM -0600, Toshi Kani wrote: > MTRR_TYPE_INVALID means MTRRs disabled. So, the caller checking with > this value is the same as checking with mtrr_enabled() you suggested.
So then you don't have to set *uniform = 1 on entry to mtrr_type_lookup(). And change the retval test
if ((!uniform) && (mtrr != MTRR_TYPE_WRBACK))
to if ((mtrr != MTRR_TYPE_INVALID) && (!uniform) && (mtrr != MTRR_TYPE_WRBACK))
You can put the MTRR_TYPE_INVALID first so that it shortcuts.
You need the distinction between MTRRs *disabled* and an MTRR region being {non-,}uniform.
If MTRRs are disabled, uniform doesn't *mean* *anything* because it is undefined. When MTRRs are disabled, the range is *not* covered by MTRRs because, well, them MTRRs are disabled.
And it might be fine for *your* use case to set *uniform even when MTRRs are disabled but it might matter in the future. So we better design it correct from the beginning.
-- Regards/Gruss, Boris.
ECO tip #101: Trim your mails when you reply. --
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