[PATCH 3/9] mm: Use common huge_ptep_get() function for riscv/arm64

[Alexandre Ghiti <alexghiti@rivosinc.com>]

For that, we need to introduce:

- a new config: ARCH_HAS_CONTPTE,
- a new arch specific function which returns the number of contiguous PTE
  in a mapping and its base page size,
- a pte_cont() helper, only introduced for riscv since we keep the arm64
  naming (contpte) which is more explicit than the riscv's (napot).

Signed-off-by: Alexandre Ghiti <alexghiti@rivosinc.com>
---
 arch/arm64/Kconfig               |  1 +
 arch/arm64/include/asm/pgtable.h | 31 ++++++++++++++++++
 arch/arm64/mm/hugetlbpage.c      | 55 ++------------------------------
 arch/riscv/Kconfig               |  1 +
 arch/riscv/include/asm/hugetlb.h |  2 +-
 arch/riscv/include/asm/pgtable.h |  1 +
 arch/riscv/mm/hugetlbpage.c      | 24 --------------
 mm/Kconfig                       |  3 ++
 mm/Makefile                      |  1 +
 mm/contpte.c                     | 45 ++++++++++++++++++++++++++
 10 files changed, 86 insertions(+), 78 deletions(-)
 create mode 100644 mm/contpte.c

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index aa7c1d435139..5e6bd49169d7 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -20,6 +20,7 @@ config ARM64
 	select ARCH_ENABLE_SPLIT_PMD_PTLOCK if PGTABLE_LEVELS > 2
 	select ARCH_ENABLE_THP_MIGRATION if TRANSPARENT_HUGEPAGE
 	select ARCH_HAS_CACHE_LINE_SIZE
+	select ARCH_HAS_CONTPTE
 	select ARCH_HAS_CURRENT_STACK_POINTER
 	select ARCH_HAS_DEBUG_VIRTUAL
 	select ARCH_HAS_DEBUG_VM_PGTABLE
diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
index 79ce70fbb751..3003a10547de 100644
--- a/arch/arm64/include/asm/pgtable.h
+++ b/arch/arm64/include/asm/pgtable.h
@@ -1124,6 +1124,37 @@ extern pte_t ptep_modify_prot_start(struct vm_area_struct *vma,
 extern void ptep_modify_prot_commit(struct vm_area_struct *vma,
 				    unsigned long addr, pte_t *ptep,
 				    pte_t old_pte, pte_t new_pte);
+
+static inline int arch_contpte_get_num_contig(pte_t *ptep, unsigned long size,
+					      size_t *pgsize)
+{
+	int contig_ptes = 0;
+
+	*pgsize = size;
+
+	switch (size) {
+#ifndef __PAGETABLE_PMD_FOLDED
+	case PUD_SIZE:
+		if (pud_sect_supported())
+			contig_ptes = 1;
+		break;
+#endif
+	case PMD_SIZE:
+		contig_ptes = 1;
+		break;
+	case CONT_PMD_SIZE:
+		*pgsize = PMD_SIZE;
+		contig_ptes = CONT_PMDS;
+		break;
+	case CONT_PTE_SIZE:
+		*pgsize = PAGE_SIZE;
+		contig_ptes = CONT_PTES;
+		break;
+	}
+
+	return contig_ptes;
+}
+
 #endif /* !__ASSEMBLY__ */
 
 #endif /* __ASM_PGTABLE_H */
diff --git a/arch/arm64/mm/hugetlbpage.c b/arch/arm64/mm/hugetlbpage.c
index 8116ac599f80..6b61714d7726 100644
--- a/arch/arm64/mm/hugetlbpage.c
+++ b/arch/arm64/mm/hugetlbpage.c
@@ -119,57 +119,6 @@ static int find_num_contig(struct mm_struct *mm, unsigned long addr,
 	return CONT_PTES;
 }
 
-static inline int num_contig_ptes(unsigned long size, size_t *pgsize)
-{
-	int contig_ptes = 0;
-
-	*pgsize = size;
-
-	switch (size) {
-#ifndef __PAGETABLE_PMD_FOLDED
-	case PUD_SIZE:
-		if (pud_sect_supported())
-			contig_ptes = 1;
-		break;
-#endif
-	case PMD_SIZE:
-		contig_ptes = 1;
-		break;
-	case CONT_PMD_SIZE:
-		*pgsize = PMD_SIZE;
-		contig_ptes = CONT_PMDS;
-		break;
-	case CONT_PTE_SIZE:
-		*pgsize = PAGE_SIZE;
-		contig_ptes = CONT_PTES;
-		break;
-	}
-
-	return contig_ptes;
-}
-
-pte_t huge_ptep_get(pte_t *ptep)
-{
-	int ncontig, i;
-	size_t pgsize;
-	pte_t orig_pte = ptep_get(ptep);
-
-	if (!pte_present(orig_pte) || !pte_cont(orig_pte))
-		return orig_pte;
-
-	ncontig = num_contig_ptes(page_size(pte_page(orig_pte)), &pgsize);
-	for (i = 0; i < ncontig; i++, ptep++) {
-		pte_t pte = ptep_get(ptep);
-
-		if (pte_dirty(pte))
-			orig_pte = pte_mkdirty(orig_pte);
-
-		if (pte_young(pte))
-			orig_pte = pte_mkyoung(orig_pte);
-	}
-	return orig_pte;
-}
-
 /*
  * Changing some bits of contiguous entries requires us to follow a
  * Break-Before-Make approach, breaking the whole contiguous set
@@ -250,7 +199,7 @@ void set_huge_pte_at(struct mm_struct *mm, unsigned long addr,
 	unsigned long pfn, dpfn;
 	pgprot_t hugeprot;
 
-	ncontig = num_contig_ptes(sz, &pgsize);
+	ncontig = arch_contpte_get_num_contig(ptep, sz, &pgsize);
 
 	if (!pte_present(pte)) {
 		for (i = 0; i < ncontig; i++, ptep++, addr += pgsize)
@@ -397,7 +346,7 @@ void huge_pte_clear(struct mm_struct *mm, unsigned long addr,
 	int i, ncontig;
 	size_t pgsize;
 
-	ncontig = num_contig_ptes(sz, &pgsize);
+	ncontig = arch_contpte_get_num_contig(NULL, sz, &pgsize);
 
 	for (i = 0; i < ncontig; i++, addr += pgsize, ptep++)
 		pte_clear(mm, addr, ptep);
diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index dba28a756e63..121183768d1a 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -19,6 +19,7 @@ config RISCV
 	select ARCH_ENABLE_SPLIT_PMD_PTLOCK if PGTABLE_LEVELS > 2
 	select ARCH_ENABLE_THP_MIGRATION if TRANSPARENT_HUGEPAGE
 	select ARCH_HAS_BINFMT_FLAT
+	select ARCH_HAS_CONTPTE if RISCV_ISA_SVNAPOT
 	select ARCH_HAS_CURRENT_STACK_POINTER
 	select ARCH_HAS_DEBUG_VIRTUAL if MMU
 	select ARCH_HAS_DEBUG_VM_PGTABLE
diff --git a/arch/riscv/include/asm/hugetlb.h b/arch/riscv/include/asm/hugetlb.h
index 20f9c3ba2341..a431a0c0e0fa 100644
--- a/arch/riscv/include/asm/hugetlb.h
+++ b/arch/riscv/include/asm/hugetlb.h
@@ -47,7 +47,7 @@ pte_t huge_ptep_get(pte_t *ptep);
 pte_t arch_make_huge_pte(pte_t entry, unsigned int shift, vm_flags_t flags);
 #define arch_make_huge_pte arch_make_huge_pte
 
-#endif /*CONFIG_RISCV_ISA_SVNAPOT*/
+#endif /* CONFIG_RISCV_ISA_SVNAPOT */
 
 #include <asm-generic/hugetlb.h>
 
diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/pgtable.h
index 951f3ceb5529..ddff4a56e12d 100644
--- a/arch/riscv/include/asm/pgtable.h
+++ b/arch/riscv/include/asm/pgtable.h
@@ -302,6 +302,7 @@ static inline unsigned long pte_napot(pte_t pte)
 {
 	return pte_val(pte) & _PAGE_NAPOT;
 }
+#define pte_cont	pte_napot
 
 #define pte_valid_napot(pte)	(pte_present(pte) && pte_napot(pte))
 
diff --git a/arch/riscv/mm/hugetlbpage.c b/arch/riscv/mm/hugetlbpage.c
index 2477d20c1497..51ec80cf2028 100644
--- a/arch/riscv/mm/hugetlbpage.c
+++ b/arch/riscv/mm/hugetlbpage.c
@@ -3,30 +3,6 @@
 #include <linux/err.h>
 
 #ifdef CONFIG_RISCV_ISA_SVNAPOT
-pte_t huge_ptep_get(pte_t *ptep)
-{
-	unsigned long pte_num;
-	int i;
-	pte_t orig_pte = ptep_get(ptep);
-
-	if (!pte_present(orig_pte) || !pte_napot(orig_pte))
-		return orig_pte;
-
-	pte_num = napot_pte_num(napot_cont_order(orig_pte));
-
-	for (i = 0; i < pte_num; i++, ptep++) {
-		pte_t pte = ptep_get(ptep);
-
-		if (pte_dirty(pte))
-			orig_pte = pte_mkdirty(orig_pte);
-
-		if (pte_young(pte))
-			orig_pte = pte_mkyoung(orig_pte);
-	}
-
-	return orig_pte;
-}
-
 pte_t *huge_pte_alloc(struct mm_struct *mm,
 		      struct vm_area_struct *vma,
 		      unsigned long addr,
diff --git a/mm/Kconfig b/mm/Kconfig
index ffc3a2ba3a8c..71d92e6c50d9 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -1001,6 +1001,9 @@ config IDLE_PAGE_TRACKING
 config ARCH_HAS_CACHE_LINE_SIZE
 	bool
 
+config ARCH_HAS_CONTPTE
+	bool
+
 config ARCH_HAS_CURRENT_STACK_POINTER
 	bool
 	help
diff --git a/mm/Makefile b/mm/Makefile
index e4b5b75aaec9..d5aa9326fc80 100644
--- a/mm/Makefile
+++ b/mm/Makefile
@@ -90,6 +90,7 @@ obj-$(CONFIG_MIGRATION) += migrate.o
 obj-$(CONFIG_NUMA) += memory-tiers.o
 obj-$(CONFIG_DEVICE_MIGRATION) += migrate_device.o
 obj-$(CONFIG_TRANSPARENT_HUGEPAGE) += huge_memory.o khugepaged.o
+obj-$(CONFIG_ARCH_HAS_CONTPTE) += contpte.o
 obj-$(CONFIG_PAGE_COUNTER) += page_counter.o
 obj-$(CONFIG_MEMCG) += memcontrol.o vmpressure.o
 ifdef CONFIG_SWAP
diff --git a/mm/contpte.c b/mm/contpte.c
new file mode 100644
index 000000000000..c3f4b8039b19
--- /dev/null
+++ b/mm/contpte.c
@@ -0,0 +1,45 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2024 Rivos Inc.
+ */
+
+#include <linux/mm.h>
+#include <linux/pgtable.h>
+#include <linux/hugetlb.h>
+
+/*
+ * Any arch that wants to use that needs to define:
+ * * contpte macros
+ *   - pte_cont()
+ *   - arch_contpte_get_num_contig()
+ */
+
+/*
+ * This file implements the following contpte aware API:
+ * huge_ptep_get()
+ */
+
+pte_t huge_ptep_get(pte_t *ptep)
+{
+	int ncontig, i;
+	size_t pgsize;
+	pte_t orig_pte = ptep_get(ptep);
+
+	if (!pte_present(orig_pte) || !pte_cont(orig_pte))
+		return orig_pte;
+
+	ncontig = arch_contpte_get_num_contig(ptep,
+					      page_size(pte_page(orig_pte)),
+					      &pgsize);
+
+	for (i = 0; i < ncontig; i++, ptep++) {
+		pte_t pte = ptep_get(ptep);
+
+		if (pte_dirty(pte))
+			orig_pte = pte_mkdirty(orig_pte);
+
+		if (pte_young(pte))
+			orig_pte = pte_mkyoung(orig_pte);
+	}
+	return orig_pte;
+}
-- 
2.39.2