+ arm64-mm-move-__check_safe_pte_update.patch added to mm-new branch

+ arm64-mm-move-__check_safe_pte_update.patch added to mm-new branch

[Andrew Morton]

The patch titled
     Subject: arm64/mm: move __check_safe_pte_update()
has been added to the -mm mm-new branch.  Its filename is
     arm64-mm-move-__check_safe_pte_update.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/arm64-mm-move-__check_safe_pte_update.patch

This patch will later appear in the mm-new branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

Note, mm-new is a provisional staging ground for work-in-progress
patches, and acceptance into mm-new is a notification for others take
notice and to finish up reviews.  Please do not hesitate to respond to
review feedback and post updated versions to replace or incrementally
fixup patches in mm-new.

The mm-new branch of mm.git is not included in linux-next

If a few days of testing in mm-new is successful, the patch will me moved
into mm.git's mm-unstable branch, which is included in linux-next

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------------------------------------------------------
From: Anshuman Khandual <anshuman.khandual@arm.com>
Subject: arm64/mm: move __check_safe_pte_update()
Date: Wed, 16 Sep 2026 10:19:32 +0530

Patch series "arm64/mm: Standardize printing for pgtable entries", v3.

Standardize printing for pgtable entries using recently introduced generic
helper ptval_bytes_to_hex_str() in core MM which automatically enables 128
bits entries when added later.

But first move __check_safe_pte_update() outside <asm/pgtable.h> to avoid
a cyclic dependency while accessing these afore mentioned core MM helpers
defined in <linux/pgtable.h>.  This replaces the original page table entry
print standardisation proposal which was part of the D128 series [1].


This patch (of 2):

The page table entry print helpers and related macros which are defined in
<linux/pgtable.h> will not be accessible in platform <asm/pgtable.h> which
is basically caused by cycling dependency.

Move __check_safe_pte_update() inside arch/arm64/mm/mmu.c as a preparation
for subsequent usage of the afore mentioned generic MM helpers.  While
here drop IS_ENABLED(CONFIG_DEBUG_VM), although wrap
__check_safe_pte_update() inside #ifdef CONFIG_DEBUG_VM that preserves the
current code optimization which is achieved via the static inline
functions.

This does not cause any functional change.

Link: https://lore.kernel.org/20260916044933.2689426-2-anshuman.khandual@arm.com
Link: https://lore.kernel.org/linux-mm/20260729122452.3797443-11-anshuman.khandual@arm.com/ [1]
Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: David Hildenbrand (Arm) <david@kernel.org>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Lorenzo Stoakes <ljs@kernel.org>
---

 arch/arm64/include/asm/pgtable.h |   49 ++---------------------------
 arch/arm64/mm/mmu.c              |   44 ++++++++++++++++++++++++++
 2 files changed, 49 insertions(+), 44 deletions(-)

--- a/arch/arm64/include/asm/pgtable.h~arm64-mm-move-__check_safe_pte_update
+++ a/arch/arm64/include/asm/pgtable.h
@@ -387,52 +387,13 @@ static inline pte_t __ptep_get(pte_t *pt
 extern void __sync_icache_dcache(pte_t pteval);
 bool pgattr_change_is_safe(pteval_t old, pteval_t new);
 
-/*
- * PTE bits configuration in the presence of hardware Dirty Bit Management
- * (PTE_WRITE == PTE_DBM):
- *
- * Dirty  Writable | PTE_RDONLY  PTE_WRITE  PTE_DIRTY (sw)
- *   0      0      |   1           0          0
- *   0      1      |   1           1          0
- *   1      0      |   1           0          1
- *   1      1      |   0           1          x
- *
- * When hardware DBM is not present, the software PTE_DIRTY bit is updated via
- * the page fault mechanism. Checking the dirty status of a pte becomes:
- *
- *   PTE_DIRTY || (PTE_WRITE && !PTE_RDONLY)
- */
-
-static inline void __check_safe_pte_update(struct mm_struct *mm, pte_t *ptep,
-					   pte_t pte)
+#ifdef CONFIG_DEBUG_VM
+void __check_safe_pte_update(struct mm_struct *mm, pte_t *ptep, pte_t pte);
+#else
+static inline void __check_safe_pte_update(struct mm_struct *mm, pte_t *ptep, pte_t pte)
 {
-	pte_t old_pte;
-
-	if (!IS_ENABLED(CONFIG_DEBUG_VM))
-		return;
-
-	old_pte = __ptep_get(ptep);
-
-	if (!pte_valid(old_pte) || !pte_valid(pte))
-		return;
-	if (mm != current->active_mm && atomic_read(&mm->mm_users) <= 1)
-		return;
-
-	/*
-	 * Check for potential race with hardware updates of the pte
-	 * (__ptep_set_access_flags safely changes valid ptes without going
-	 * through an invalid entry).
-	 */
-	VM_WARN_ONCE(!pte_young(pte),
-		     "%s: racy access flag clearing: 0x%016llx -> 0x%016llx",
-		     __func__, pte_val(old_pte), pte_val(pte));
-	VM_WARN_ONCE(pte_write(old_pte) && !pte_dirty(pte),
-		     "%s: racy dirty state clearing: 0x%016llx -> 0x%016llx",
-		     __func__, pte_val(old_pte), pte_val(pte));
-	VM_WARN_ONCE(!pgattr_change_is_safe(pte_val(old_pte), pte_val(pte)),
-		     "%s: unsafe attribute change: 0x%016llx -> 0x%016llx",
-		     __func__, pte_val(old_pte), pte_val(pte));
 }
+#endif /* CONFIG_DEBUG_VM */
 
 static inline void __sync_cache_and_tags(pte_t pte, unsigned int nr_pages)
 {
--- a/arch/arm64/mm/mmu.c~arm64-mm-move-__check_safe_pte_update
+++ a/arch/arm64/mm/mmu.c
@@ -2392,4 +2392,48 @@ int arch_set_user_pkey_access(int pkey,
 
 	return 0;
 }
+
+/*
+ * PTE bits configuration in the presence of hardware Dirty Bit Management
+ * (PTE_WRITE == PTE_DBM):
+ *
+ * Dirty  Writable | PTE_RDONLY  PTE_WRITE  PTE_DIRTY (sw)
+ *   0      0      |   1           0          0
+ *   0      1      |   1           1          0
+ *   1      0      |   1           0          1
+ *   1      1      |   0           1          x
+ *
+ * When hardware DBM is not present, the software PTE_DIRTY bit is updated via
+ * the page fault mechanism. Checking the dirty status of a pte becomes:
+ *
+ *   PTE_DIRTY || (PTE_WRITE && !PTE_RDONLY)
+ */
+#ifdef CONFIG_DEBUG_VM
+void __check_safe_pte_update(struct mm_struct *mm, pte_t *ptep, pte_t pte)
+{
+	pte_t old_pte;
+
+	old_pte = __ptep_get(ptep);
+
+	if (!pte_valid(old_pte) || !pte_valid(pte))
+		return;
+	if (mm != current->active_mm && atomic_read(&mm->mm_users) <= 1)
+		return;
+
+	/*
+	 * Check for potential race with hardware updates of the pte
+	 * (__ptep_set_access_flags safely changes valid ptes without going
+	 * through an invalid entry).
+	 */
+	VM_WARN_ONCE(!pte_young(pte),
+		     "%s: racy access flag clearing: 0x%016llx -> 0x%016llx",
+		     __func__, pte_val(old_pte), pte_val(pte));
+	VM_WARN_ONCE(pte_write(old_pte) && !pte_dirty(pte),
+		     "%s: racy dirty state clearing: 0x%016llx -> 0x%016llx",
+		     __func__, pte_val(old_pte), pte_val(pte));
+	VM_WARN_ONCE(!pgattr_change_is_safe(pte_val(old_pte), pte_val(pte)),
+		     "%s: unsafe attribute change: 0x%016llx -> 0x%016llx",
+		     __func__, pte_val(old_pte), pte_val(pte));
+}
+#endif /* CONFIG_DEBUG_VM */
 #endif
_

Patches currently in -mm which might be from anshuman.khandual@arm.com are

mm-make-ptval_to_str-generally-available.patch
mm-stop-using-pxd_error.patch
loongarch-mm-stop-using-pte_error.patch
parisc-mm-directly-use-generic-_clear_bad.patch
sh-mm-stop-using-pte_error.patch
sh-mm-stop-using-_error.patch
sh-mm-stop-using-pgd_error.patch
mm-drop-pxd_error.patch
mm-constify-arguments-in-default-pxdp_get.patch
arm64-mm-move-__check_safe_pte_update.patch
arm64-mm-standardize-printing-for-pgtable-entries.patch