From b3890c0f96f3f0eadaa954069949ac3ef8f3bbbe Mon Sep 17 00:00:00 2001
From: Kalesh Singh <kaleshsingh@google.com>
Date: Mon, 7 Nov 2022 16:05:00 -0800
Subject: [PATCH] Revert "FROMLIST: mm: x86, arm64: add
 arch_has_hw_pte_young()"

This reverts commit 1861f17391a871ecf944fd504cbb906fc6121261.

To be replaced with upstream version.

Bug: 249601646
Change-Id: Ib992a9f199a9f30fbbf3f39537d87a8fb605c893
Signed-off-by: Kalesh Singh <kaleshsingh@google.com>
---
 arch/arm64/include/asm/pgtable.h | 14 ++++++++++++--
 arch/x86/include/asm/pgtable.h   |  6 +++---
 include/linux/pgtable.h          | 13 -------------
 mm/memory.c                      | 14 +++++++++++++-
 4 files changed, 28 insertions(+), 19 deletions(-)

diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
index d1b19eaf9479..e2a304ef1fea 100644
--- a/arch/arm64/include/asm/pgtable.h
+++ b/arch/arm64/include/asm/pgtable.h
@@ -1008,13 +1008,23 @@ static inline void update_mmu_cache(struct vm_area_struct *vma,
  * page after fork() + CoW for pfn mappings. We don't always have a
  * hardware-managed access flag on arm64.
  */
-#define arch_has_hw_pte_young		cpu_has_hw_af
+static inline bool arch_faults_on_old_pte(void)
+{
+	WARN_ON(preemptible());
+
+	return !cpu_has_hw_af();
+}
+#define arch_faults_on_old_pte		arch_faults_on_old_pte
 
 /*
  * Experimentally, it's cheap to set the access flag in hardware and we
  * benefit from prefaulting mappings as 'old' to start with.
  */
-#define arch_wants_old_prefaulted_pte	cpu_has_hw_af
+static inline bool arch_wants_old_prefaulted_pte(void)
+{
+	return !arch_faults_on_old_pte();
+}
+#define arch_wants_old_prefaulted_pte	arch_wants_old_prefaulted_pte
 
 #endif /* !__ASSEMBLY__ */
 
diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h
index 3908780fc408..448cd01eb3ec 100644
--- a/arch/x86/include/asm/pgtable.h
+++ b/arch/x86/include/asm/pgtable.h
@@ -1397,10 +1397,10 @@ 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)
+#define arch_faults_on_old_pte arch_faults_on_old_pte
+static inline bool arch_faults_on_old_pte(void)
 {
-	return true;
+	return false;
 }
 
 #endif	/* __ASSEMBLY__ */
diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h
index 2f1188980baf..d468efcf48f4 100644
--- a/include/linux/pgtable.h
+++ b/include/linux/pgtable.h
@@ -259,19 +259,6 @@ static inline int pmdp_clear_flush_young(struct vm_area_struct *vma,
 #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
 #endif
 
-#ifndef arch_has_hw_pte_young
-/*
- * Return whether the accessed bit is supported on the local CPU.
- *
- * This stub assumes accessing through an old PTE triggers a page fault.
- * Architectures that automatically set the access bit should overwrite it.
- */
-static inline bool arch_has_hw_pte_young(void)
-{
-	return false;
-}
-#endif
-
 #ifndef __HAVE_ARCH_PTEP_GET_AND_CLEAR
 static inline pte_t ptep_get_and_clear(struct mm_struct *mm,
 				       unsigned long address,
diff --git a/mm/memory.c b/mm/memory.c
index 84a45b664c48..dbeff9cf9604 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -122,6 +122,18 @@ int randomize_va_space __read_mostly =
 					2;
 #endif
 
+#ifndef arch_faults_on_old_pte
+static inline bool arch_faults_on_old_pte(void)
+{
+	/*
+	 * Those arches which don't have hw access flag feature need to
+	 * implement their own helper. By default, "true" means pagefault
+	 * will be hit on old pte.
+	 */
+	return true;
+}
+#endif
+
 #ifndef arch_wants_old_prefaulted_pte
 static inline bool arch_wants_old_prefaulted_pte(void)
 {
@@ -2904,7 +2916,7 @@ static inline bool cow_user_page(struct page *dst, struct page *src,
 	 * On architectures with software "accessed" bits, we would
 	 * take a double page fault, so mark it accessed here.
 	 */
-	if (!arch_has_hw_pte_young() && !pte_young(vmf->orig_pte)) {
+	if (arch_faults_on_old_pte() && !pte_young(vmf->orig_pte)) {
 		pte_t entry;
 
 		vmf->pte = pte_offset_map_lock(mm, vmf->pmd, addr, &vmf->ptl);