* Borislav Petkov <bp@xxxxxxxxx> wrote: > --- a/arch/x86/mm/pgtable.c > +++ b/arch/x86/mm/pgtable.c > @@ -566,19 +566,28 @@ 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 any of the following conditions are met: > + * > + * - 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. > + * > + * Callers should try to decrease page size (1GB -> 2MB -> 4K) if the bigger > + * page mapping attempt fails. This comment should explain why it's ok in the WB case. Also, the phrase 'the memory type of the range' is ambiguous: it might mean the partial MTRR's, or the memory type specified via PAT by the huge-pmd entry. Thanks, Ingo -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>