diff options
Diffstat (limited to 'include/linux')
| -rw-r--r-- | include/linux/pgtable.h | 32 |
1 files changed, 22 insertions, 10 deletions
diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h index 3df6db1e9e39..8c093c119e5a 100644 --- a/include/linux/pgtable.h +++ b/include/linux/pgtable.h @@ -2110,18 +2110,26 @@ static inline int pud_trans_unstable(pud_t *pud) return 0; } -#ifndef CONFIG_NUMA_BALANCING +#ifndef CONFIG_ARCH_HAS_PTE_PROTNONE /* - * In an inaccessible (PROT_NONE) VMA, pte_protnone() may indicate "yes". It is - * perfectly valid to indicate "no" in that case, which is why our default - * implementation defaults to "always no". + * In an inaccessible (PROT_NONE) VMA, pte_protnone() may indicate "yes". It + * is perfectly valid to indicate "no" in that case, which is why our + * default implementation defaults to "always no". * - * In an accessible VMA, however, pte_protnone() reliably indicates PROT_NONE - * page protection due to NUMA hinting. NUMA hinting faults only apply in - * accessible VMAs. + * In an accessible VMA, pte_protnone() reliably indicates a present + * PROT_NONE page protection. Today the kernel uses such PTEs for two + * purposes: NUMA hinting faults, and userfaultfd RWP tracking on + * VM_UFFD_RWP VMAs. The two are distinguished by the uffd PTE bit and + * the VMA flag; see include/linux/userfaultfd_k.h. * - * So, to reliably identify PROT_NONE PTEs that require a NUMA hinting fault, - * looking at the VMA accessibility is sufficient. + * So, to reliably identify PROT_NONE PTEs that require kernel handling, + * looking at the VMA accessibility (and the uffd bit on RWP VMAs) is + * sufficient. + * + * Architectures without CONFIG_ARCH_HAS_PTE_PROTNONE get the always-zero + * stubs below; PAGE_NONE references that survive to runtime fire the + * BUILD_BUG() fallback, since callers should have folded such paths to + * dead code via IS_ENABLED(CONFIG_ARCH_HAS_PTE_PROTNONE). */ static inline int pte_protnone(pte_t pte) { @@ -2132,7 +2140,11 @@ static inline int pmd_protnone(pmd_t pmd) { return 0; } -#endif /* CONFIG_NUMA_BALANCING */ + +#ifndef PAGE_NONE +#define PAGE_NONE ({ BUILD_BUG(); (pgprot_t){0}; }) +#endif +#endif /* CONFIG_ARCH_HAS_PTE_PROTNONE */ #endif /* CONFIG_MMU */ |