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Date: Thu, 20 May 2021 00:53:45 -0600
From: Yu Zhao <yuzhao@...gle.com>
To: linux-mm@...ck.org
Cc: Alex Shi <alexs@...nel.org>, Andi Kleen <ak@...ux.intel.com>,
Andrew Morton <akpm@...ux-foundation.org>,
Dave Chinner <david@...morbit.com>,
Dave Hansen <dave.hansen@...ux.intel.com>,
Donald Carr <sirspudd@...il.com>,
Hillf Danton <hdanton@...a.com>, Jens Axboe <axboe@...nel.dk>,
Johannes Weiner <hannes@...xchg.org>,
Jonathan Corbet <corbet@....net>,
Joonsoo Kim <iamjoonsoo.kim@....com>,
Konstantin Kharlamov <hi-angel@...dex.ru>,
Marcus Seyfarth <m.seyfarth@...il.com>,
Matthew Wilcox <willy@...radead.org>,
Mel Gorman <mgorman@...e.de>,
Miaohe Lin <linmiaohe@...wei.com>,
Michael Larabel <michael@...haellarabel.com>,
Michal Hocko <mhocko@...e.com>,
Michel Lespinasse <michel@...pinasse.org>,
Rik van Riel <riel@...riel.com>,
Roman Gushchin <guro@...com>,
Tim Chen <tim.c.chen@...ux.intel.com>,
Vlastimil Babka <vbabka@...e.cz>,
Yang Shi <shy828301@...il.com>,
Ying Huang <ying.huang@...el.com>, Zi Yan <ziy@...dia.com>,
linux-kernel@...r.kernel.org, lkp@...ts.01.org,
page-reclaim@...gle.com, Yu Zhao <yuzhao@...gle.com>,
Konstantin Kharlamov <Hi-Angel@...dex.ru>
Subject: [PATCH v3 04/14] mm, x86: support the access bit on non-leaf PMD entries
Some architectures support the accessed bit on non-leaf PMD entries
(parents) in addition to leaf PTE entries (children) where pages are
mapped, e.g., x86_64 sets the accessed bit on a parent when using it
as part of linear-address translation [1]. Page table walkers who are
interested in the accessed bit on children can take advantage of this:
they do not need to search the children when the accessed bit is not
set on a parent, given that they have previously cleared the accessed
bit on this parent.
[1]: Intel 64 and IA-32 Architectures Software Developer's Manual
Volume 3 (October 2019), section 4.8
Signed-off-by: Yu Zhao <yuzhao@...gle.com>
Tested-by: Konstantin Kharlamov <Hi-Angel@...dex.ru>
---
arch/Kconfig | 9 +++++++++
arch/x86/Kconfig | 1 +
arch/x86/include/asm/pgtable.h | 2 +-
arch/x86/mm/pgtable.c | 5 ++++-
include/linux/pgtable.h | 4 ++--
5 files changed, 17 insertions(+), 4 deletions(-)
diff --git a/arch/Kconfig b/arch/Kconfig
index c45b770d3579..e3812adc69f7 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -826,6 +826,15 @@ config HAVE_ARCH_TRANSPARENT_HUGEPAGE
config HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
bool
+config HAVE_ARCH_PARENT_PMD_YOUNG
+ bool
+ depends on PGTABLE_LEVELS > 2
+ help
+ Architectures that select this are able to set the accessed bit on
+ non-leaf PMD entries in addition to leaf PTE entries where pages are
+ mapped. For them, page table walkers that clear the accessed bit may
+ stop at non-leaf PMD entries if they do not see the accessed bit.
+
config HAVE_ARCH_HUGE_VMAP
bool
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 0045e1b44190..f619055c4537 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -170,6 +170,7 @@ config X86
select HAVE_ARCH_TRACEHOOK
select HAVE_ARCH_TRANSPARENT_HUGEPAGE
select HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD if X86_64
+ select HAVE_ARCH_PARENT_PMD_YOUNG if X86_64
select HAVE_ARCH_USERFAULTFD_WP if X86_64 && USERFAULTFD
select HAVE_ARCH_USERFAULTFD_MINOR if X86_64 && USERFAULTFD
select HAVE_ARCH_VMAP_STACK if X86_64
diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h
index b1099f2d9800..3a24d2af4e9b 100644
--- a/arch/x86/include/asm/pgtable.h
+++ b/arch/x86/include/asm/pgtable.h
@@ -846,7 +846,7 @@ static inline unsigned long pmd_page_vaddr(pmd_t pmd)
static inline int pmd_bad(pmd_t pmd)
{
- return (pmd_flags(pmd) & ~_PAGE_USER) != _KERNPG_TABLE;
+ return ((pmd_flags(pmd) | _PAGE_ACCESSED) & ~_PAGE_USER) != _KERNPG_TABLE;
}
static inline unsigned long pages_to_mb(unsigned long npg)
diff --git a/arch/x86/mm/pgtable.c b/arch/x86/mm/pgtable.c
index d27cf69e811d..b968d6bd28b6 100644
--- a/arch/x86/mm/pgtable.c
+++ b/arch/x86/mm/pgtable.c
@@ -550,7 +550,7 @@ int ptep_test_and_clear_young(struct vm_area_struct *vma,
return ret;
}
-#ifdef CONFIG_TRANSPARENT_HUGEPAGE
+#if defined(CONFIG_TRANSPARENT_HUGEPAGE) || defined(CONFIG_HAVE_ARCH_PARENT_PMD_YOUNG)
int pmdp_test_and_clear_young(struct vm_area_struct *vma,
unsigned long addr, pmd_t *pmdp)
{
@@ -562,6 +562,9 @@ int pmdp_test_and_clear_young(struct vm_area_struct *vma,
return ret;
}
+#endif
+
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
int pudp_test_and_clear_young(struct vm_area_struct *vma,
unsigned long addr, pud_t *pudp)
{
diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h
index 46b13780c2c8..94ecc1d277a2 100644
--- a/include/linux/pgtable.h
+++ b/include/linux/pgtable.h
@@ -193,7 +193,7 @@ static inline int ptep_test_and_clear_young(struct vm_area_struct *vma,
#endif
#ifndef __HAVE_ARCH_PMDP_TEST_AND_CLEAR_YOUNG
-#ifdef CONFIG_TRANSPARENT_HUGEPAGE
+#if defined(CONFIG_TRANSPARENT_HUGEPAGE) || defined(CONFIG_HAVE_ARCH_PARENT_PMD_YOUNG)
static inline int pmdp_test_and_clear_young(struct vm_area_struct *vma,
unsigned long address,
pmd_t *pmdp)
@@ -214,7 +214,7 @@ static inline int pmdp_test_and_clear_young(struct vm_area_struct *vma,
BUILD_BUG();
return 0;
}
-#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
+#endif /* CONFIG_TRANSPARENT_HUGEPAGE || CONFIG_HAVE_ARCH_PARENT_PMD_YOUNG */
#endif
#ifndef __HAVE_ARCH_PTEP_CLEAR_YOUNG_FLUSH
--
2.31.1.751.gd2f1c929bd-goog
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