linux-kernel - [PATCH v1 08/14] arm64/mm: ptep_set_access_flags(): New layer to manage contig bit

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Message-Id: <20230622144210.2623299-9-ryan.roberts@arm.com>
Date:   Thu, 22 Jun 2023 15:42:03 +0100
From:   Ryan Roberts <ryan.roberts@....com>
To:     Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Ard Biesheuvel <ardb@...nel.org>,
        Marc Zyngier <maz@...nel.org>,
        Oliver Upton <oliver.upton@...ux.dev>,
        James Morse <james.morse@....com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Zenghui Yu <yuzenghui@...wei.com>,
        Andrey Ryabinin <ryabinin.a.a@...il.com>,
        Alexander Potapenko <glider@...gle.com>,
        Andrey Konovalov <andreyknvl@...il.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Vincenzo Frascino <vincenzo.frascino@....com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Anshuman Khandual <anshuman.khandual@....com>,
        Matthew Wilcox <willy@...radead.org>,
        Yu Zhao <yuzhao@...gle.com>,
        Mark Rutland <mark.rutland@....com>
Cc:     Ryan Roberts <ryan.roberts@....com>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org
Subject: [PATCH v1 08/14] arm64/mm: ptep_set_access_flags(): New layer to manage contig bit

Create a new layer for the in-table PTE manipulation APIs. For now, The
existing API is prefixed with double underscore to become the
arch-private API and the public API is just a simple wrapper that calls
the private API.

The public API implementation will subsequently be used to transparently
manipulate the contiguous bit where appropriate. But since there are
already some contig-aware users (e.g. hugetlb, kernel mapper), we must
first ensure those users use the private API directly so that the future
contig-bit manipulations in the public API do not interfere with those
existing uses.

No behavioural changes intended.

Signed-off-by: Ryan Roberts <ryan.roberts@....com>
---
 arch/arm64/include/asm/pgtable.h | 16 ++++++++++++----
 arch/arm64/mm/fault.c            |  6 +++---
 arch/arm64/mm/hugetlbpage.c      |  2 +-
 3 files changed, 16 insertions(+), 8 deletions(-)

diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
index 2fcc3b19c873..ff79578fd806 100644
--- a/arch/arm64/include/asm/pgtable.h
+++ b/arch/arm64/include/asm/pgtable.h
@@ -311,7 +311,7 @@ static inline void __check_safe_pte_update(struct mm_struct *mm, pte_t *ptep,
 
 	/*
 	 * Check for potential race with hardware updates of the pte
-	 * (ptep_set_access_flags safely changes valid ptes without going
+	 * (__ptep_set_access_flags safely changes valid ptes without going
 	 * through an invalid entry).
 	 */
 	VM_WARN_ONCE(!pte_young(pte),
@@ -842,8 +842,7 @@ static inline pmd_t pmd_modify(pmd_t pmd, pgprot_t newprot)
 	return pte_pmd(pte_modify(pmd_pte(pmd), newprot));
 }
 
-#define __HAVE_ARCH_PTEP_SET_ACCESS_FLAGS
-extern int ptep_set_access_flags(struct vm_area_struct *vma,
+extern int __ptep_set_access_flags(struct vm_area_struct *vma,
 				 unsigned long address, pte_t *ptep,
 				 pte_t entry, int dirty);
 
@@ -853,7 +852,8 @@ static inline int pmdp_set_access_flags(struct vm_area_struct *vma,
 					unsigned long address, pmd_t *pmdp,
 					pmd_t entry, int dirty)
 {
-	return ptep_set_access_flags(vma, address, (pte_t *)pmdp, pmd_pte(entry), dirty);
+	return __ptep_set_access_flags(vma, address, (pte_t *)pmdp,
+							pmd_pte(entry), dirty);
 }
 
 static inline int pud_devmap(pud_t pud)
@@ -1166,6 +1166,14 @@ static inline void ptep_set_wrprotect(struct mm_struct *mm,
 	__ptep_set_wrprotect(mm, addr, ptep);
 }
 
+#define __HAVE_ARCH_PTEP_SET_ACCESS_FLAGS
+static inline int ptep_set_access_flags(struct vm_area_struct *vma,
+				unsigned long addr, pte_t *ptep,
+				pte_t entry, int dirty)
+{
+	return __ptep_set_access_flags(vma, addr, ptep, entry, dirty);
+}
+
 #endif /* !__ASSEMBLY__ */
 
 #endif /* __ASM_PGTABLE_H */
diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c
index d3a64624ed88..f5a7a5ff6814 100644
--- a/arch/arm64/mm/fault.c
+++ b/arch/arm64/mm/fault.c
@@ -195,9 +195,9 @@ static void show_pte(unsigned long addr)
  *
  * Returns whether or not the PTE actually changed.
  */
-int ptep_set_access_flags(struct vm_area_struct *vma,
-			  unsigned long address, pte_t *ptep,
-			  pte_t entry, int dirty)
+int __ptep_set_access_flags(struct vm_area_struct *vma,
+			    unsigned long address, pte_t *ptep,
+			    pte_t entry, int dirty)
 {
 	pteval_t old_pteval, pteval;
 	pte_t pte = READ_ONCE(*ptep);
diff --git a/arch/arm64/mm/hugetlbpage.c b/arch/arm64/mm/hugetlbpage.c
index 7d5eb71db396..9a87b1c5661a 100644
--- a/arch/arm64/mm/hugetlbpage.c
+++ b/arch/arm64/mm/hugetlbpage.c
@@ -477,7 +477,7 @@ int huge_ptep_set_access_flags(struct vm_area_struct *vma,
 	pte_t orig_pte;
 
 	if (!pte_cont(pte))
-		return ptep_set_access_flags(vma, addr, ptep, pte, dirty);
+		return __ptep_set_access_flags(vma, addr, ptep, pte, dirty);
 
 	ncontig = find_num_contig(mm, addr, ptep, &pgsize);
 	dpfn = pgsize >> PAGE_SHIFT;
-- 
2.25.1