Messages in this thread | | | Date | Mon, 18 May 2015 21:01:50 +0200 | From | Borislav Petkov <> | Subject | Re: [PATCH v5 6/6] mtrr, mm, x86: Enhance MTRR checks for KVA huge page mapping |
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On Mon, May 18, 2015 at 11:22:39AM -0600, Toshi Kani wrote: > > diff --git a/arch/x86/mm/pgtable.c b/arch/x86/mm/pgtable.c > > index c30f9819786b..f1894daa79ee 100644 > > --- a/arch/x86/mm/pgtable.c > > +++ b/arch/x86/mm/pgtable.c > > @@ -566,19 +566,24 @@ void native_set_fixmap(enum fixed_addresses idx, phys_addr_t phys, > > /** > > * pud_set_huge - setup kernel PUD mapping > > * > > - * MTRR can override PAT memory types with 4KiB granularity. Therefore, > > - * this function does not set up a huge page when the range is covered > > - * by a non-WB type of MTRR. MTRR_TYPE_INVALID indicates that MTRR are > > - * disabled. > > + * MTRRs can override PAT memory types with 4KiB granularity. Therefore, > > + * this function sets up a huge page only if all of the following > > + * conditions are met: > > It should be "if any of the following condition is met". Or, does NOT > setup if all of ... > > > + * > > + * - MTRRs are disabled. > > + * - The range is mapped uniformly by an MTRR, i.e. the range is > > + * fully covered by a single MTRR entry or the default type. > > + * - The MTRR memory type is WB.
Hmm, ok, so this is kinda like "any" but they also depend on each other. So it is
If - MTRRs are disabled
or
- MTRRs are enabled and the range is completely covered by a single MTRR
or
- MTRRs are enabled and the range is not completely covered by a single MTRR but the memory type of the range is WB, even if covered by multiple MTRRs.
Right?
So tell me this: why do we need to repeat that over those KVA helpers? It's not like the callers can do anything about it, can they?
So maybe that comment - expanded into more detail - should be over mtrr_type_lookup() only. That'll be better, methinks.
Hmm.
-- Regards/Gruss, Boris.
ECO tip #101: Trim your mails when you reply. --
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