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@xxxxxxxxxxxxxxx>
Reviewed-by: Rick Edgecombe <rick.p.edgecombe@xxxxxxxxx>
Reviewed-by: Baoquan He <bhe@xxxxxxxxxx>
Reviewed-by: Dave Hansen <dave.hansen@xxxxxxxxx>
Tested-by: Tao Liu <ltao@xxxxxxxxxx>
---
arch/x86/include/asm/pgtable_types.h | 1 +
arch/x86/mm/pat/set_memory.c | 21 ++++++++++-----------
2 files changed, 11 insertions(+), 11 deletions(-)
diff --git a/arch/x86/include/asm/pgtable_types.h b/arch/x86/include/asm/pgtable_types.h
index b78644962626..2f321137736c 100644
--- a/arch/x86/include/asm/pgtable_types.h
+++ b/arch/x86/include/asm/pgtable_types.h
@@ -549,6 +549,7 @@ 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 498812f067cd..a7a7a6c6a3fb 100644
--- a/arch/x86/mm/pat/set_memory.c
+++ b/arch/x86/mm/pat/set_memory.c
@@ -662,8 +662,9 @@ 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, the level of the mapping, and the effective
- * NX and RW bits of all page table levels.
+ * Return a pointer to the entry (or NULL if the entry does not exist),
+ * the level of the entry, and the effective NX and RW bits of all
+ * page table levels.
*/
pte_t *lookup_address_in_pgd_attr(pgd_t *pgd, unsigned long address,
unsigned int *level, bool *nx, bool *rw)
@@ -672,13 +673,14 @@ pte_t *lookup_address_in_pgd_attr(pgd_t *pgd, unsigned long address,
pud_t *pud;
pmd_t *pmd;
- *level = PG_LEVEL_NONE;
+ *level = PG_LEVEL_256T;
*nx = false;
*rw = true;
if (pgd_none(*pgd))
return NULL;
+ *level = PG_LEVEL_512G;
*nx |= pgd_flags(*pgd) & _PAGE_NX;
*rw &= pgd_flags(*pgd) & _PAGE_RW;
@@ -686,10 +688,10 @@ pte_t *lookup_address_in_pgd_attr(pgd_t *pgd, unsigned long address,
if (p4d_none(*p4d))
return NULL;
- *level = PG_LEVEL_512G;
if (p4d_leaf(*p4d) || !p4d_present(*p4d))
return (pte_t *)p4d;
+ *level = PG_LEVEL_1G;
*nx |= p4d_flags(*p4d) & _PAGE_NX;
*rw &= p4d_flags(*p4d) & _PAGE_RW;
@@ -697,10 +699,10 @@ pte_t *lookup_address_in_pgd_attr(pgd_t *pgd, unsigned long address,
if (pud_none(*pud))
return NULL;
- *level = PG_LEVEL_1G;
if (pud_leaf(*pud) || !pud_present(*pud))
return (pte_t *)pud;
+ *level = PG_LEVEL_2M;
*nx |= pud_flags(*pud) & _PAGE_NX;
*rw &= pud_flags(*pud) & _PAGE_RW;
@@ -708,15 +710,13 @@ pte_t *lookup_address_in_pgd_attr(pgd_t *pgd, unsigned long address,
if (pmd_none(*pmd))
return NULL;
- *level = PG_LEVEL_2M;
if (pmd_leaf(*pmd) || !pmd_present(*pmd))
return (pte_t *)pmd;
+ *level = PG_LEVEL_4K;
*nx |= pmd_flags(*pmd) & _PAGE_NX;
*rw &= pmd_flags(*pmd) & _PAGE_RW;
- *level = PG_LEVEL_4K;
-
return pte_offset_kernel(pmd, address);
}
@@ -736,9 +736,8 @@ 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
