diff options
| -rw-r--r-- | include/asm-x86/pgtable.h | 5 |
1 files changed, 5 insertions, 0 deletions
diff --git a/include/asm-x86/pgtable.h b/include/asm-x86/pgtable.h index a1eeacdf9d8c..75a656e6b3f8 100644 --- a/include/asm-x86/pgtable.h +++ b/include/asm-x86/pgtable.h @@ -19,6 +19,11 @@ #define _PAGE_BIT_UNUSED3 11 #define _PAGE_BIT_NX 63 /* No execute: only valid after cpuid check */ +/* + * Note: we use _AC(1, L) instead of _AC(1, UL) so that we get a + * sign-extended value on 32-bit with all 1's in the upper word, + * which preserves the upper pte values on 64-bit ptes: + */ #define _PAGE_PRESENT (_AC(1, L)<<_PAGE_BIT_PRESENT) #define _PAGE_RW (_AC(1, L)<<_PAGE_BIT_RW) #define _PAGE_USER (_AC(1, L)<<_PAGE_BIT_USER) |