linux-kernel - [RFC PATCH v2 10/21] riscv: mm: Reimplement PTE A/D bit check function

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Message-Id: <20241205103729.14798-11-luxu.kernel@bytedance.com>
Date: Thu,  5 Dec 2024 18:37:18 +0800
From: Xu Lu <luxu.kernel@...edance.com>
To: paul.walmsley@...ive.com,
	palmer@...belt.com,
	aou@...s.berkeley.edu,
	ardb@...nel.org,
	anup@...infault.org,
	atishp@...shpatra.org
Cc: xieyongji@...edance.com,
	lihangjing@...edance.com,
	punit.agrawal@...edance.com,
	linux-kernel@...r.kernel.org,
	linux-riscv@...ts.infradead.org,
	Xu Lu <luxu.kernel@...edance.com>
Subject: [RFC PATCH v2 10/21] riscv: mm: Reimplement PTE A/D bit check function

CPU that supports only 4K MMU usually updates access/dirty bit at 4K pte
level. As each software page can contains multiple 4K hardware pages, we need
to traverse all mapping entries to check whether corresponding 4K page
is accessed or dirty during pte_dirty/pte_access functions.

Signed-off-by: Xu Lu <luxu.kernel@...edance.com>
---
 arch/riscv/include/asm/pgtable.h | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/pgtable.h
index bf724d006236..c0f7442c8a9e 100644
--- a/arch/riscv/include/asm/pgtable.h
+++ b/arch/riscv/include/asm/pgtable.h
@@ -553,6 +553,29 @@ static inline int pte_huge(pte_t pte)
 	return pte_present(pte) && (pte_val(pte) & _PAGE_LEAF);
 }
 
+#ifdef CONFIG_RISCV_USE_SW_PAGE
+static inline int pte_dirty(pte_t pte)
+{
+	unsigned int i;
+
+	for (i = 0; i < HW_PAGES_PER_PAGE; i++)
+		if (pte.ptes[i] & _PAGE_DIRTY)
+			return 1;
+
+	return 0;
+}
+
+static inline int pte_young(pte_t pte)
+{
+	unsigned int i;
+
+	for (i = 0; i < HW_PAGES_PER_PAGE; i++)
+		if (pte.ptes[i] & _PAGE_ACCESSED)
+			return 1;
+
+	return 0;
+}
+#else
 static inline int pte_dirty(pte_t pte)
 {
 	return pte_val(pte) & _PAGE_DIRTY;
@@ -562,6 +585,7 @@ static inline int pte_young(pte_t pte)
 {
 	return pte_val(pte) & _PAGE_ACCESSED;
 }
+#endif /* CONFIG_RISCV_USE_SW_PAGE */
 
 static inline int pte_special(pte_t pte)
 {
-- 
2.20.1