diff options
| -rw-r--r-- | arch/x86/include/asm/pgtable_types.h | 20 |
1 files changed, 20 insertions, 0 deletions
diff --git a/arch/x86/include/asm/pgtable_types.h b/arch/x86/include/asm/pgtable_types.h index ec8a1fc9505d..3c32db8c539d 100644 --- a/arch/x86/include/asm/pgtable_types.h +++ b/arch/x86/include/asm/pgtable_types.h @@ -64,6 +64,26 @@ #define _PAGE_FILE (_AT(pteval_t, 1) << _PAGE_BIT_FILE) #define _PAGE_PROTNONE (_AT(pteval_t, 1) << _PAGE_BIT_PROTNONE) +/* + * _PAGE_NUMA indicates that this page will trigger a numa hinting + * minor page fault to gather numa placement statistics (see + * pte_numa()). The bit picked (8) is within the range between + * _PAGE_FILE (6) and _PAGE_PROTNONE (8) bits. Therefore, it doesn't + * require changes to the swp entry format because that bit is always + * zero when the pte is not present. + * + * The bit picked must be always zero when the pmd is present and not + * present, so that we don't lose information when we set it while + * atomically clearing the present bit. + * + * Because we shared the same bit (8) with _PAGE_PROTNONE this can be + * interpreted as _PAGE_NUMA only in places that _PAGE_PROTNONE + * couldn't reach, like handle_mm_fault() (see access_error in + * arch/x86/mm/fault.c, the vma protection must not be PROT_NONE for + * handle_mm_fault() to be invoked). + */ +#define _PAGE_NUMA _PAGE_PROTNONE + #define _PAGE_TABLE (_PAGE_PRESENT | _PAGE_RW | _PAGE_USER | \ _PAGE_ACCESSED | _PAGE_DIRTY) #define _KERNPG_TABLE (_PAGE_PRESENT | _PAGE_RW | _PAGE_ACCESSED | \ |