diff options
Diffstat (limited to 'arch/x86/include/asm/pgtable_64.h')
| -rw-r--r-- | arch/x86/include/asm/pgtable_64.h | 12 |
1 files changed, 9 insertions, 3 deletions
diff --git a/arch/x86/include/asm/pgtable_64.h b/arch/x86/include/asm/pgtable_64.h index 2160c1fee920..46bf71c77a25 100644 --- a/arch/x86/include/asm/pgtable_64.h +++ b/arch/x86/include/asm/pgtable_64.h @@ -180,15 +180,21 @@ static inline int pgd_large(pgd_t pgd) { return 0; } /* * Encode and de-code a swap entry * - * | ... | 11| 10| 9|8|7|6|5| 4| 3|2|1|0| <- bit number - * | ... |SW3|SW2|SW1|G|L|D|A|CD|WT|U|W|P| <- bit names - * | OFFSET (14->63) | TYPE (9-13) |0|X|X|X| X| X|X|X|0| <- swp entry + * | ... | 11| 10| 9|8|7|6|5| 4| 3|2| 1|0| <- bit number + * | ... |SW3|SW2|SW1|G|L|D|A|CD|WT|U| W|P| <- bit names + * | OFFSET (14->63) | TYPE (9-13) |0|0|X|X| X| X|X|SD|0| <- swp entry * * G (8) is aliased and used as a PROT_NONE indicator for * !present ptes. We need to start storing swap entries above * there. We also need to avoid using A and D because of an * erratum where they can be incorrectly set by hardware on * non-present PTEs. + * + * SD (1) in swp entry is used to store soft dirty bit, which helps us + * remember soft dirty over page migration + * + * Bit 7 in swp entry should be 0 because pmd_present checks not only P, + * but also L and G. */ #define SWP_TYPE_FIRST_BIT (_PAGE_BIT_PROTNONE + 1) #define SWP_TYPE_BITS 5 |