Messages in this thread Patch in this message | | | From | "Kirill A. Shutemov" <> | Subject | [PATCHv8 07/17] x86/mm: Return correct level from lookup_address() if pte is none | Date | Tue, 27 Feb 2024 23:24:42 +0200 |
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Currently, lookup_address() returns two things: 1. A "pte_t" (which might be a p[g4um]d_t) 2. The 'level' of the page tables where the "pte_t" was found (returned via a pointer)
If no pte_t is found, 'level' is essentially garbage.
Always fill out the level. For NULL "pte_t"s, fill in the level where the p*d_none() entry was found mirroring the "found" behavior.
Always filling out the level allows using lookup_address() to precisely skip over holes when walking kernel page tables.
Add one more entry into enum pg_level to indicate the size of the VA covered by one PGD entry in 5-level paging mode.
Update comments for lookup_address() and lookup_address_in_pgd() to reflect changes in the interface.
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Reviewed-by: Rick Edgecombe <rick.p.edgecombe@intel.com> Reviewed-by: Baoquan He <bhe@redhat.com> Reviewed-by: Dave Hansen <dave.hansen@intel.com> --- arch/x86/include/asm/pgtable_types.h | 1 + arch/x86/mm/pat/set_memory.c | 16 ++++++++-------- 2 files changed, 9 insertions(+), 8 deletions(-)
diff --git a/arch/x86/include/asm/pgtable_types.h b/arch/x86/include/asm/pgtable_types.h index 0b748ee16b3d..3f648ffdfbe5 100644 --- a/arch/x86/include/asm/pgtable_types.h +++ b/arch/x86/include/asm/pgtable_types.h @@ -548,6 +548,7 @@ enum pg_level { PG_LEVEL_2M, PG_LEVEL_1G, PG_LEVEL_512G, + PG_LEVEL_256T, PG_LEVEL_NUM }; diff --git a/arch/x86/mm/pat/set_memory.c b/arch/x86/mm/pat/set_memory.c index f92da8c9a86d..0d2267ad4e0e 100644 --- a/arch/x86/mm/pat/set_memory.c +++ b/arch/x86/mm/pat/set_memory.c @@ -657,7 +657,8 @@ static inline pgprot_t verify_rwx(pgprot_t old, pgprot_t new, unsigned long star /* * Lookup the page table entry for a virtual address in a specific pgd. - * Return a pointer to the entry and the level of the mapping. + * Return a pointer to the entry (or NULL if the entry does not exist) and + * the level of the entry. */ pte_t *lookup_address_in_pgd(pgd_t *pgd, unsigned long address, unsigned int *level) @@ -666,32 +667,32 @@ pte_t *lookup_address_in_pgd(pgd_t *pgd, unsigned long address, pud_t *pud; pmd_t *pmd; - *level = PG_LEVEL_NONE; + *level = PG_LEVEL_256T; if (pgd_none(*pgd)) return NULL; + *level = PG_LEVEL_512G; p4d = p4d_offset(pgd, address); if (p4d_none(*p4d)) return NULL; - *level = PG_LEVEL_512G; if (p4d_large(*p4d) || !p4d_present(*p4d)) return (pte_t *)p4d; + *level = PG_LEVEL_1G; pud = pud_offset(p4d, address); if (pud_none(*pud)) return NULL; - *level = PG_LEVEL_1G; if (pud_large(*pud) || !pud_present(*pud)) return (pte_t *)pud; + *level = PG_LEVEL_2M; pmd = pmd_offset(pud, address); if (pmd_none(*pmd)) return NULL; - *level = PG_LEVEL_2M; if (pmd_large(*pmd) || !pmd_present(*pmd)) return (pte_t *)pmd; @@ -704,9 +705,8 @@ pte_t *lookup_address_in_pgd(pgd_t *pgd, unsigned long address, * Lookup the page table entry for a virtual address. Return a pointer * to the entry and the level of the mapping. * - * Note: We return pud and pmd either when the entry is marked large - * or when the present bit is not set. Otherwise we would return a - * pointer to a nonexisting mapping. + * Note: the function returns p4d, pud or pmd either when the entry is marked + * large or when the present bit is not set. Otherwise it returns NULL. */ pte_t *lookup_address(unsigned long address, unsigned int *level) { -- 2.43.0
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