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Subject[PATCH V2 3/3] Documentation/mm: Add descriptions for arch page table helpers
Date
This removes existing description from the test and instead adds a specific
description file for all arch page table helpers which is in sync with the
semantics being tested via CONFIG_DEBUG_VM_PGTABLE. All future changes
either to these descriptions here or the debug test should always remain
in sync.

Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: linux-doc@vger.kernel.org
Cc: linux-mm@kvack.org
Cc: linux-kernel@vger.kernel.org
Suggested-by: Mike Rapoport <rppt@kernel.org>
Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
---
Documentation/vm/arch_pgtable_helpers.rst | 256 ++++++++++++++++++++++
mm/debug_vm_pgtable.c | 13 +-
2 files changed, 259 insertions(+), 10 deletions(-)
create mode 100644 Documentation/vm/arch_pgtable_helpers.rst

diff --git a/Documentation/vm/arch_pgtable_helpers.rst b/Documentation/vm/arch_pgtable_helpers.rst
new file mode 100644
index 000000000000..1fc8a1d8932a
--- /dev/null
+++ b/Documentation/vm/arch_pgtable_helpers.rst
@@ -0,0 +1,256 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+.. _arch_page_table_helpers:
+
+===============================
+Architecture Page Table Helpers
+===============================
+
+Generic MM expects architectures (with MMU) to provide helpers to create, access
+and modify page table entries at various level for different memory functions.
+These page table helpers need to conform to a common semantics across platforms.
+Following tables describe the expected semantics which can also be tested during
+boot via CONFIG_DEBUG_VM_PGTABLE option. All future changes in here or the debug
+test need to be in sync.
+
+======================
+PTE Page Table Helpers
+======================
+
+--------------------------------------------------------------------------------
+| pte_same | Tests whether both PTE entries are the same |
+--------------------------------------------------------------------------------
+| pte_bad | Tests a non-table mapped PTE |
+--------------------------------------------------------------------------------
+| pte_present | Tests a valid mapped PTE |
+--------------------------------------------------------------------------------
+| pte_young | Tests a young PTE |
+--------------------------------------------------------------------------------
+| pte_dirty | Tests a dirty PTE |
+--------------------------------------------------------------------------------
+| pte_write | Tests a writable PTE |
+--------------------------------------------------------------------------------
+| pte_special | Tests a special PTE |
+--------------------------------------------------------------------------------
+| pte_protnone | Tests a PROT_NONE PTE |
+--------------------------------------------------------------------------------
+| pte_devmap | Tests a ZONE_DEVICE mapped PTE |
+--------------------------------------------------------------------------------
+| pte_soft_dirty | Tests a soft dirty PTE |
+--------------------------------------------------------------------------------
+| pte_swp_soft_dirty | Tests a soft dirty swapped PTE |
+--------------------------------------------------------------------------------
+| pte_mkyoung | Creates a young PTE |
+--------------------------------------------------------------------------------
+| pte_mkold | Creates an old PTE |
+--------------------------------------------------------------------------------
+| pte_mkdirty | Creates a dirty PTE |
+--------------------------------------------------------------------------------
+| pte_mkclean | Creates a clean PTE |
+--------------------------------------------------------------------------------
+| pte_mkwrite | Creates a writable PTE |
+--------------------------------------------------------------------------------
+| pte_mkwrprotect | Creates a write protected PTE |
+--------------------------------------------------------------------------------
+| pte_mkspecial | Creates a special PTE |
+--------------------------------------------------------------------------------
+| pte_mkdevmap | Creates a ZONE_DEVICE mapped PTE |
+--------------------------------------------------------------------------------
+| pte_mksoft_dirty | Creates a soft dirty PTE |
+--------------------------------------------------------------------------------
+| pte_clear_soft_dirty | Clears a soft dirty PTE |
+--------------------------------------------------------------------------------
+| pte_swp_mksoft_dirty | Creates a soft dirty swapped PTE |
+--------------------------------------------------------------------------------
+| pte_swp_clear_soft_dirty | Clears a soft dirty swapped PTE |
+--------------------------------------------------------------------------------
+| pte_mknotpresent | Invalidates a mapped PTE |
+--------------------------------------------------------------------------------
+| ptep_get_and_clear | Clears a PTE |
+--------------------------------------------------------------------------------
+| ptep_get_and_clear_full | Clears a PTE |
+--------------------------------------------------------------------------------
+| ptep_test_and_clear_young | Clears young from a PTE |
+--------------------------------------------------------------------------------
+| ptep_set_wrprotect | Converts into a write protected PTE |
+--------------------------------------------------------------------------------
+| ptep_set_access_flags | Converts into a more permissive PTE |
+--------------------------------------------------------------------------------
+
+======================
+PMD Page Table Helpers
+======================
+
+--------------------------------------------------------------------------------
+| pmd_same | Tests whether both PMD entries are the same |
+--------------------------------------------------------------------------------
+| pmd_bad | Tests a non-table mapped PMD |
+--------------------------------------------------------------------------------
+| pmd_leaf | Tests a leaf mapped PMD |
+--------------------------------------------------------------------------------
+| pmd_huge | Tests a HugeTLB mapped PMD |
+--------------------------------------------------------------------------------
+| pmd_trans_huge | Tests a Transparent Huge Page (THP) at PMD |
+--------------------------------------------------------------------------------
+| pmd_present | Tests a valid mapped PMD |
+--------------------------------------------------------------------------------
+| pmd_young | Tests a young PMD |
+--------------------------------------------------------------------------------
+| pmd_dirty | Tests a dirty PMD |
+--------------------------------------------------------------------------------
+| pmd_write | Tests a writable PMD |
+--------------------------------------------------------------------------------
+| pmd_special | Tests a special PMD |
+--------------------------------------------------------------------------------
+| pmd_protnone | Tests a PROT_NONE PMD |
+--------------------------------------------------------------------------------
+| pmd_devmap | Tests a ZONE_DEVICE mapped PMD |
+--------------------------------------------------------------------------------
+| pmd_soft_dirty | Tests a soft dirty PMD |
+--------------------------------------------------------------------------------
+| pmd_swp_soft_dirty | Tests a soft dirty swapped PMD |
+--------------------------------------------------------------------------------
+| pmd_mkyoung | Creates a young PMD |
+--------------------------------------------------------------------------------
+| pmd_mkold | Creates an old PMD |
+--------------------------------------------------------------------------------
+| pmd_mkdirty | Creates a dirty PMD |
+--------------------------------------------------------------------------------
+| pmd_mkclean | Creates a clean PMD |
+--------------------------------------------------------------------------------
+| pmd_mkwrite | Creates a writable PMD |
+--------------------------------------------------------------------------------
+| pmd_mkwrprotect | Creates a write protected PMD |
+--------------------------------------------------------------------------------
+| pmd_mkspecial | Creates a special PMD |
+--------------------------------------------------------------------------------
+| pmd_mkdevmap | Creates a ZONE_DEVICE mapped PMD |
+--------------------------------------------------------------------------------
+| pmd_mksoft_dirty | Creates a soft dirty PMD |
+--------------------------------------------------------------------------------
+| pmd_clear_soft_dirty | Clears a soft dirty PMD |
+--------------------------------------------------------------------------------
+| pmd_swp_mksoft_dirty | Creates a soft dirty swapped PMD |
+--------------------------------------------------------------------------------
+| pmd_swp_clear_soft_dirty | Clears a soft dirty swapped PMD |
+--------------------------------------------------------------------------------
+| pmd_mknotpresent | Invalidates a mapped PMD |
+--------------------------------------------------------------------------------
+| pmd_set_huge | Creates a PMD huge mapping |
+--------------------------------------------------------------------------------
+| pmd_clear_huge | Clears a PMD huge mapping |
+--------------------------------------------------------------------------------
+| pmdp_get_and_clear | Clears a PMD |
+--------------------------------------------------------------------------------
+| pmdp_get_and_clear_full | Clears a PMD |
+--------------------------------------------------------------------------------
+| pmdp_test_and_clear_young | Clears young from a PMD |
+--------------------------------------------------------------------------------
+| pmdp_set_wrprotect | Converts into a write protected PMD |
+--------------------------------------------------------------------------------
+| pmdp_set_access_flags | Converts into a more permissive PMD |
+--------------------------------------------------------------------------------
+
+======================
+PUD Page Table Helpers
+======================
+
+--------------------------------------------------------------------------------
+| pud_same | Tests whether both PUD entries are the same |
+--------------------------------------------------------------------------------
+| pud_bad | Tests a non-table mapped PUD |
+--------------------------------------------------------------------------------
+| pud_leaf | Tests a leaf mapped PUD |
+--------------------------------------------------------------------------------
+| pud_huge | Tests a HugeTLB mapped PUD |
+--------------------------------------------------------------------------------
+| pud_trans_huge | Tests a Transparent Huge Page (THP) at PUD |
+--------------------------------------------------------------------------------
+| pud_present | Tests a valid mapped PUD |
+--------------------------------------------------------------------------------
+| pud_young | Tests a young PUD |
+--------------------------------------------------------------------------------
+| pud_dirty | Tests a dirty PUD |
+--------------------------------------------------------------------------------
+| pud_write | Tests a writable PUD |
+--------------------------------------------------------------------------------
+| pud_devmap | Tests a ZONE_DEVICE mapped PUD |
+--------------------------------------------------------------------------------
+| pud_mkyoung | Creates a young PUD |
+--------------------------------------------------------------------------------
+| pud_mkold | Creates an old PUD |
+--------------------------------------------------------------------------------
+| pud_mkdirty | Creates a dirty PUD |
+--------------------------------------------------------------------------------
+| pud_mkclean | Creates a clean PUD |
+--------------------------------------------------------------------------------
+| pud_mkwrite | Creates a writable PMD |
+--------------------------------------------------------------------------------
+| pud_mkwrprotect | Creates a write protected PMD |
+--------------------------------------------------------------------------------
+| pud_mkdevmap | Creates a ZONE_DEVICE mapped PMD |
+--------------------------------------------------------------------------------
+| pud_mknotpresent | Invalidates a mapped PUD |
+--------------------------------------------------------------------------------
+| pud_set_huge | Creates a PUD huge mapping |
+--------------------------------------------------------------------------------
+| pud_clear_huge | Clears a PUD huge mapping |
+--------------------------------------------------------------------------------
+| pudp_get_and_clear | Clears a PUD |
+--------------------------------------------------------------------------------
+| pudp_get_and_clear_full | Clears a PUD |
+--------------------------------------------------------------------------------
+| pudp_test_and_clear_young | Clears young from a PUD |
+--------------------------------------------------------------------------------
+| pudp_set_wrprotect | Converts into a write protected PUD |
+--------------------------------------------------------------------------------
+| pudp_set_access_flags | Converts into a more permissive PUD |
+--------------------------------------------------------------------------------
+
+==========================
+HugeTLB Page Table Helpers
+==========================
+
+--------------------------------------------------------------------------------
+| pte_huge | Tests a HugeTLB |
+--------------------------------------------------------------------------------
+| pte_mkhuge | Creates a HugeTLB |
+--------------------------------------------------------------------------------
+| huge_pte_dirty | Tests a dirty HugeTLB |
+--------------------------------------------------------------------------------
+| huge_pte_write | Tests a writable HugeTLB |
+--------------------------------------------------------------------------------
+| huge_pte_mkdirty | Creates a dirty HugeTLB |
+--------------------------------------------------------------------------------
+| huge_pte_mkwrite | Creates a writable HugeTLB |
+--------------------------------------------------------------------------------
+| huge_pte_mkwrprotect | Creates a write protected HugeTLB |
+--------------------------------------------------------------------------------
+| huge_ptep_get_and_clear | Clears a HugeTLB |
+--------------------------------------------------------------------------------
+| huge_ptep_set_wrprotect | Converts into a write protected HugeTLB |
+--------------------------------------------------------------------------------
+| huge_ptep_set_access_flags | Converts into a more permissive HugeTLB |
+--------------------------------------------------------------------------------
+
+========================
+SWAP Page Table Helpers
+========================
+
+--------------------------------------------------------------------------------
+| __pte_to_swp_entry | Creates a swapped entry (arch) from a mapepd PTE |
+--------------------------------------------------------------------------------
+| __swp_to_pte_entry | Creates a mapped PTE from a swapped entry (arch) |
+--------------------------------------------------------------------------------
+| __pmd_to_swp_entry | Creates a swapped entry (arch) from a mapepd PMD |
+--------------------------------------------------------------------------------
+| __swp_to_pmd_entry | Creates a mapped PMD from a swapped entry (arch) |
+--------------------------------------------------------------------------------
+| is_migration_entry | Tests a migration (read or write) swapped entry |
+--------------------------------------------------------------------------------
+| is_write_migration_entry | Tests a write migration swapped entry |
+--------------------------------------------------------------------------------
+| make_migration_entry_read | Converts into read migration swapped entry |
+--------------------------------------------------------------------------------
+| make_migration_entry | Creates a migration swapped entry (read or write)|
+--------------------------------------------------------------------------------
diff --git a/mm/debug_vm_pgtable.c b/mm/debug_vm_pgtable.c
index 87b4b495333b..7c210f99a812 100644
--- a/mm/debug_vm_pgtable.c
+++ b/mm/debug_vm_pgtable.c
@@ -32,16 +32,9 @@
#include <asm/tlbflush.h>

/*
- * Basic operations
- *
- * mkold(entry) = An old and not a young entry
- * mkyoung(entry) = A young and not an old entry
- * mkdirty(entry) = A dirty and not a clean entry
- * mkclean(entry) = A clean and not a dirty entry
- * mkwrite(entry) = A write and not a write protected entry
- * wrprotect(entry) = A write protected and not a write entry
- * pxx_bad(entry) = A mapped and non-table entry
- * pxx_same(entry1, entry2) = Both entries hold the exact same value
+ * Please refer Documentation/vm/arch_pgtable_helpers.rst for the semantics
+ * expectations that are being validated here. All future changes in here
+ * or the documentation need to be in sync.
*/
#define VMFLAGS (VM_READ|VM_WRITE|VM_EXEC)

--
2.20.1
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