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Date: Wed, 20 Dec 2023 04:00:34 +0000
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Subject: [PATCH mm-unstable v1 1/4] mm/mglru: add CONFIG_ARCH_HAS_HW_PTE_YOUNG
From: Kinsey Ho <kinseyho@google.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, yuzhao@google.com, 
	Kinsey Ho <kinseyho@google.com>, Aneesh Kumar K V <aneesh.kumar@linux.ibm.com>
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Some architectures are able to set the accessed bit in PTEs when PTEs
are used as part of linear address translations.

Add CONFIG_ARCH_HAS_HW_PTE_YOUNG for such architectures to be able to
override arch_has_hw_pte_young().

Signed-off-by: Kinsey Ho <kinseyho@google.com>
Co-developed-by: Aneesh Kumar K V <aneesh.kumar@linux.ibm.com>
Signed-off-by: Aneesh Kumar K V <aneesh.kumar@linux.ibm.com>
---
 arch/Kconfig                   | 8 ++++++++
 arch/arm64/Kconfig             | 1 +
 arch/x86/Kconfig               | 1 +
 arch/x86/include/asm/pgtable.h | 6 ------
 include/linux/pgtable.h        | 2 +-
 5 files changed, 11 insertions(+), 7 deletions(-)

diff --git a/arch/Kconfig b/arch/Kconfig
index f4b210ab0612..8c8901f80586 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -1470,6 +1470,14 @@ config DYNAMIC_SIGFRAME
 config HAVE_ARCH_NODE_DEV_GROUP
 	bool
 
+config ARCH_HAS_HW_PTE_YOUNG
+	bool
+	help
+	  Architectures that select this option are capable of setting the
+	  accessed bit in PTE entries when using them as part of linear address
+	  translations. Architectures that require runtime check should select
+	  this option and override arch_has_hw_pte_young().
+
 config ARCH_HAS_NONLEAF_PMD_YOUNG
 	bool
 	help
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 7b071a00425d..12d611f3da5d 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -36,6 +36,7 @@ config ARM64
 	select ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
 	select ARCH_HAS_PTE_DEVMAP
 	select ARCH_HAS_PTE_SPECIAL
+	select ARCH_HAS_HW_PTE_YOUNG
 	select ARCH_HAS_SETUP_DMA_OPS
 	select ARCH_HAS_SET_DIRECT_MAP
 	select ARCH_HAS_SET_MEMORY
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 1566748f16c4..04941a1ffc0a 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -88,6 +88,7 @@ config X86
 	select ARCH_HAS_PMEM_API		if X86_64
 	select ARCH_HAS_PTE_DEVMAP		if X86_64
 	select ARCH_HAS_PTE_SPECIAL
+	select ARCH_HAS_HW_PTE_YOUNG
 	select ARCH_HAS_NONLEAF_PMD_YOUNG	if PGTABLE_LEVELS > 2
 	select ARCH_HAS_UACCESS_FLUSHCACHE	if X86_64
 	select ARCH_HAS_COPY_MC			if X86_64
diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h
index 57bab91bbf50..08b5cb22d9a6 100644
--- a/arch/x86/include/asm/pgtable.h
+++ b/arch/x86/include/asm/pgtable.h
@@ -1679,12 +1679,6 @@ static inline bool arch_has_pfn_modify_check(void)
 	return boot_cpu_has_bug(X86_BUG_L1TF);
 }
 
-#define arch_has_hw_pte_young arch_has_hw_pte_young
-static inline bool arch_has_hw_pte_young(void)
-{
-	return true;
-}
-
 #define arch_check_zapped_pte arch_check_zapped_pte
 void arch_check_zapped_pte(struct vm_area_struct *vma, pte_t pte);
 
diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h
index af7639c3b0a3..9ecc20fa6269 100644
--- a/include/linux/pgtable.h
+++ b/include/linux/pgtable.h
@@ -375,7 +375,7 @@ static inline bool arch_has_hw_nonleaf_pmd_young(void)
  */
 static inline bool arch_has_hw_pte_young(void)
 {
-	return false;
+	return IS_ENABLED(CONFIG_ARCH_HAS_HW_PTE_YOUNG);
 }
 #endif
 
-- 
2.43.0.472.g3155946c3a-goog