target/linux/generic/pending-5.15/020-01-mm-x86-add-CONFIG_ARCH_HAS_NONLEAF_PMD_YOUNG.patch

   1 From f8b663bbfa30af5515e222fd74df20ea4e8393a2 Mon Sep 17 00:00:00 2001
   2 From: Yu Zhao <yuzhao@google.com>
   3 Date: Sat, 26 Sep 2020 21:17:18 -0600
   4 Subject: [PATCH 02/10] mm: x86: add CONFIG_ARCH_HAS_NONLEAF_PMD_YOUNG
   5
   6 Some architectures support the accessed bit on non-leaf PMD entries,
   7 e.g., x86_64 sets the accessed bit on a non-leaf PMD entry when using
   8 it as part of linear address translation [1]. As an optimization, page
   9 table walkers who are interested in the accessed bit can skip the PTEs
  10 under a non-leaf PMD entry if the accessed bit is cleared on this PMD
  11 entry.
  12
  13 Although an inline function may be preferable, this capability is
  14 added as a configuration option to look consistent when used with the
  15 existing macros.
  16
  17 [1]: Intel 64 and IA-32 Architectures Software Developer's Manual
  18      Volume 3 (June 2021), section 4.8
  19
  20 Signed-off-by: Yu Zhao <yuzhao@google.com>
  21 Tested-by: Konstantin Kharlamov <Hi-Angel@yandex.ru>
  22 Change-Id: I1a17be3ae926f721f7b17ea1539e5c39e8c4f9a8
  23 ---
  24  arch/Kconfig                   | 9 +++++++++
  25  arch/x86/Kconfig               | 1 +
  26  arch/x86/include/asm/pgtable.h | 3 ++-
  27  arch/x86/mm/pgtable.c          | 5 ++++-
  28  include/linux/pgtable.h        | 4 ++--
  29  5 files changed, 18 insertions(+), 4 deletions(-)
  30
  31 --- a/arch/Kconfig
  32 +++ b/arch/Kconfig
  33 @@ -1295,6 +1295,15 @@ config ARCH_HAS_ELFCORE_COMPAT
  34  config ARCH_HAS_PARANOID_L1D_FLUSH
  35         bool
  36
  37 +config ARCH_HAS_NONLEAF_PMD_YOUNG
  38 +       bool
  39 +       depends on PGTABLE_LEVELS > 2
  40 +       help
  41 +         Architectures that select this are able to set the accessed bit on
  42 +         non-leaf PMD entries in addition to leaf PTE entries where pages are
  43 +         mapped. For them, page table walkers that clear the accessed bit may
  44 +         stop at non-leaf PMD entries if they do not see the accessed bit.
  45 +
  46  source "kernel/gcov/Kconfig"
  47
  48  source "scripts/gcc-plugins/Kconfig"
  49 --- a/arch/x86/Kconfig
  50 +++ b/arch/x86/Kconfig
  51 @@ -84,6 +84,7 @@ config X86
  52         select ARCH_HAS_PMEM_API                if X86_64
  53         select ARCH_HAS_PTE_DEVMAP              if X86_64
  54         select ARCH_HAS_PTE_SPECIAL
  55 +       select ARCH_HAS_NONLEAF_PMD_YOUNG       if X86_64
  56         select ARCH_HAS_UACCESS_FLUSHCACHE      if X86_64
  57         select ARCH_HAS_COPY_MC                 if X86_64
  58         select ARCH_HAS_SET_MEMORY
  59 --- a/arch/x86/include/asm/pgtable.h
  60 +++ b/arch/x86/include/asm/pgtable.h
  61 @@ -817,7 +817,8 @@ static inline unsigned long pmd_page_vad
  62
  63  static inline int pmd_bad(pmd_t pmd)
  64  {
  65 -       return (pmd_flags(pmd) & ~_PAGE_USER) != _KERNPG_TABLE;
  66 +       return (pmd_flags(pmd) & ~(_PAGE_USER | _PAGE_ACCESSED)) !=
  67 +              (_KERNPG_TABLE & ~_PAGE_ACCESSED);
  68  }
  69
  70  static inline unsigned long pages_to_mb(unsigned long npg)
  71 --- a/arch/x86/mm/pgtable.c
  72 +++ b/arch/x86/mm/pgtable.c
  73 @@ -550,7 +550,7 @@ int ptep_test_and_clear_young(struct vm_
  74         return ret;
  75  }
  76
  77 -#ifdef CONFIG_TRANSPARENT_HUGEPAGE
  78 +#if defined(CONFIG_TRANSPARENT_HUGEPAGE) || defined(CONFIG_ARCH_HAS_NONLEAF_PMD_YOUNG)
  79  int pmdp_test_and_clear_young(struct vm_area_struct *vma,
  80                               unsigned long addr, pmd_t *pmdp)
  81  {
  82 @@ -562,6 +562,9 @@ int pmdp_test_and_clear_young(struct vm_
  83
  84         return ret;
  85  }
  86 +#endif
  87 +
  88 +#ifdef CONFIG_TRANSPARENT_HUGEPAGE
  89  int pudp_test_and_clear_young(struct vm_area_struct *vma,
  90                               unsigned long addr, pud_t *pudp)
  91  {
  92 --- a/include/linux/pgtable.h
  93 +++ b/include/linux/pgtable.h
  94 @@ -212,7 +212,7 @@ static inline int ptep_test_and_clear_yo
  95  #endif
  96
  97  #ifndef __HAVE_ARCH_PMDP_TEST_AND_CLEAR_YOUNG
  98 -#ifdef CONFIG_TRANSPARENT_HUGEPAGE
  99 +#if defined(CONFIG_TRANSPARENT_HUGEPAGE) || defined(CONFIG_ARCH_HAS_NONLEAF_PMD_YOUNG)
 100  static inline int pmdp_test_and_clear_young(struct vm_area_struct *vma,
 101                                             unsigned long address,
 102                                             pmd_t *pmdp)
 103 @@ -233,7 +233,7 @@ static inline int pmdp_test_and_clear_yo
 104         BUILD_BUG();
 105         return 0;
 106  }
 107 -#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
 108 +#endif /* CONFIG_TRANSPARENT_HUGEPAGE || CONFIG_ARCH_HAS_NONLEAF_PMD_YOUNG */
 109  #endif
 110
 111  #ifndef __HAVE_ARCH_PTEP_CLEAR_YOUNG_FLUSH