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Message-Id: <20240416033457.32154-3-ioworker0@gmail.com>
Date: Tue, 16 Apr 2024 11:34:56 +0800
From: Lance Yang <ioworker0@...il.com>
To: akpm@...ux-foundation.org
Cc: ryan.roberts@....com,
david@...hat.com,
21cnbao@...il.com,
mhocko@...e.com,
fengwei.yin@...el.com,
zokeefe@...gle.com,
shy828301@...il.com,
xiehuan09@...il.com,
wangkefeng.wang@...wei.com,
songmuchun@...edance.com,
peterx@...hat.com,
minchan@...nel.org,
linux-mm@...ck.org,
linux-kernel@...r.kernel.org,
Lance Yang <ioworker0@...il.com>
Subject: [PATCH v7 2/3] mm/arm64: override clear_young_dirty_ptes() batch helper
The per-pte get_and_clear/modify/set approach would result in
unfolding/refolding for contpte mappings on arm64. So we need
to override clear_young_dirty_ptes() for arm64 to avoid it.
Suggested-by: David Hildenbrand <david@...hat.com>
Suggested-by: Barry Song <21cnbao@...il.com>
Suggested-by: Ryan Roberts <ryan.roberts@....com>
Signed-off-by: Lance Yang <ioworker0@...il.com>
---
arch/arm64/include/asm/pgtable.h | 55 ++++++++++++++++++++++++++++++++
arch/arm64/mm/contpte.c | 29 +++++++++++++++++
2 files changed, 84 insertions(+)
diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
index 9fd8613b2db2..1303d30287dc 100644
--- a/arch/arm64/include/asm/pgtable.h
+++ b/arch/arm64/include/asm/pgtable.h
@@ -1223,6 +1223,46 @@ static inline void __wrprotect_ptes(struct mm_struct *mm, unsigned long address,
__ptep_set_wrprotect(mm, address, ptep);
}
+static inline void __clear_young_dirty_pte(struct vm_area_struct *vma,
+ unsigned long addr, pte_t *ptep,
+ pte_t pte, cydp_t flags)
+{
+ pte_t old_pte;
+
+ do {
+ old_pte = pte;
+
+ if (flags & CYDP_CLEAR_YOUNG)
+ pte = pte_mkold(pte);
+ if (flags & CYDP_CLEAR_DIRTY)
+ pte = pte_mkclean(pte);
+
+ pte_val(pte) = cmpxchg_relaxed(&pte_val(*ptep),
+ pte_val(old_pte), pte_val(pte));
+ } while (pte_val(pte) != pte_val(old_pte));
+}
+
+static inline void __clear_young_dirty_ptes(struct vm_area_struct *vma,
+ unsigned long addr, pte_t *ptep,
+ unsigned int nr, cydp_t flags)
+{
+ pte_t pte;
+
+ for (;;) {
+ pte = __ptep_get(ptep);
+
+ if (flags == (CYDP_CLEAR_YOUNG | CYDP_CLEAR_DIRTY))
+ __set_pte(ptep, pte_mkclean(pte_mkold(pte)));
+ else
+ __clear_young_dirty_pte(vma, addr, ptep, pte, flags);
+
+ if (--nr == 0)
+ break;
+ ptep++;
+ addr += PAGE_SIZE;
+ }
+}
+
#ifdef CONFIG_TRANSPARENT_HUGEPAGE
#define __HAVE_ARCH_PMDP_SET_WRPROTECT
static inline void pmdp_set_wrprotect(struct mm_struct *mm,
@@ -1379,6 +1419,9 @@ extern void contpte_wrprotect_ptes(struct mm_struct *mm, unsigned long addr,
extern int contpte_ptep_set_access_flags(struct vm_area_struct *vma,
unsigned long addr, pte_t *ptep,
pte_t entry, int dirty);
+extern void contpte_clear_young_dirty_ptes(struct vm_area_struct *vma,
+ unsigned long addr, pte_t *ptep,
+ unsigned int nr, cydp_t flags);
static __always_inline void contpte_try_fold(struct mm_struct *mm,
unsigned long addr, pte_t *ptep, pte_t pte)
@@ -1603,6 +1646,17 @@ static inline int ptep_set_access_flags(struct vm_area_struct *vma,
return contpte_ptep_set_access_flags(vma, addr, ptep, entry, dirty);
}
+#define clear_young_dirty_ptes clear_young_dirty_ptes
+static inline void clear_young_dirty_ptes(struct vm_area_struct *vma,
+ unsigned long addr, pte_t *ptep,
+ unsigned int nr, cydp_t flags)
+{
+ if (likely(nr == 1 && !pte_cont(__ptep_get(ptep))))
+ __clear_young_dirty_ptes(vma, addr, ptep, nr, flags);
+ else
+ contpte_clear_young_dirty_ptes(vma, addr, ptep, nr, flags);
+}
+
#else /* CONFIG_ARM64_CONTPTE */
#define ptep_get __ptep_get
@@ -1622,6 +1676,7 @@ static inline int ptep_set_access_flags(struct vm_area_struct *vma,
#define wrprotect_ptes __wrprotect_ptes
#define __HAVE_ARCH_PTEP_SET_ACCESS_FLAGS
#define ptep_set_access_flags __ptep_set_access_flags
+#define clear_young_dirty_ptes __clear_young_dirty_ptes
#endif /* CONFIG_ARM64_CONTPTE */
diff --git a/arch/arm64/mm/contpte.c b/arch/arm64/mm/contpte.c
index 1b64b4c3f8bf..9f9486de0004 100644
--- a/arch/arm64/mm/contpte.c
+++ b/arch/arm64/mm/contpte.c
@@ -361,6 +361,35 @@ void contpte_wrprotect_ptes(struct mm_struct *mm, unsigned long addr,
}
EXPORT_SYMBOL_GPL(contpte_wrprotect_ptes);
+void contpte_clear_young_dirty_ptes(struct vm_area_struct *vma,
+ unsigned long addr, pte_t *ptep,
+ unsigned int nr, cydp_t flags)
+{
+ /*
+ * We can safely clear access/dirty without needing to unfold from
+ * the architectures perspective, even when contpte is set. If the
+ * range starts or ends midway through a contpte block, we can just
+ * expand to include the full contpte block. While this is not
+ * exactly what the core-mm asked for, it tracks access/dirty per
+ * folio, not per page. And since we only create a contpte block
+ * when it is covered by a single folio, we can get away with
+ * clearing access/dirty for the whole block.
+ */
+ unsigned long start = addr;
+ unsigned long end = start + nr;
+
+ if (pte_cont(__ptep_get(ptep + nr - 1)))
+ end = ALIGN(end, CONT_PTE_SIZE);
+
+ if (pte_cont(__ptep_get(ptep))) {
+ start = ALIGN_DOWN(start, CONT_PTE_SIZE);
+ ptep = contpte_align_down(ptep);
+ }
+
+ __clear_young_dirty_ptes(vma, start, ptep, end - start, flags);
+}
+EXPORT_SYMBOL_GPL(contpte_clear_young_dirty_ptes);
+
int contpte_ptep_set_access_flags(struct vm_area_struct *vma,
unsigned long addr, pte_t *ptep,
pte_t entry, int dirty)
--
2.33.1
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