target/linux/generic/backport-5.15/020-v6.1-18-mm-introduce-arch_has_hw_nonleaf_pmd_young.patch

   1 From 46cbda7b65998a5af4493f745d94417af697bd68 Mon Sep 17 00:00:00 2001
   2 From: Juergen Gross <jgross@suse.com>
   3 Date: Wed, 23 Nov 2022 07:45:10 +0100
   4 Subject: [PATCH 18/29] mm: introduce arch_has_hw_nonleaf_pmd_young()
   5
   6 When running as a Xen PV guests commit eed9a328aa1a ("mm: x86: add
   7 CONFIG_ARCH_HAS_NONLEAF_PMD_YOUNG") can cause a protection violation in
   8 pmdp_test_and_clear_young():
   9
  10  BUG: unable to handle page fault for address: ffff8880083374d0
  11  #PF: supervisor write access in kernel mode
  12  #PF: error_code(0x0003) - permissions violation
  13  PGD 3026067 P4D 3026067 PUD 3027067 PMD 7fee5067 PTE 8010000008337065
  14  Oops: 0003 [#1] PREEMPT SMP NOPTI
  15  CPU: 7 PID: 158 Comm: kswapd0 Not tainted 6.1.0-rc5-20221118-doflr+ #1
  16  RIP: e030:pmdp_test_and_clear_young+0x25/0x40
  17
  18 This happens because the Xen hypervisor can't emulate direct writes to
  19 page table entries other than PTEs.
  20
  21 This can easily be fixed by introducing arch_has_hw_nonleaf_pmd_young()
  22 similar to arch_has_hw_pte_young() and test that instead of
  23 CONFIG_ARCH_HAS_NONLEAF_PMD_YOUNG.
  24
  25 Link: https://lkml.kernel.org/r/20221123064510.16225-1-jgross@suse.com
  26 Fixes: eed9a328aa1a ("mm: x86: add CONFIG_ARCH_HAS_NONLEAF_PMD_YOUNG")
  27 Signed-off-by: Juergen Gross <jgross@suse.com>
  28 Reported-by: Sander Eikelenboom <linux@eikelenboom.it>
  29 Acked-by: Yu Zhao <yuzhao@google.com>
  30 Tested-by: Sander Eikelenboom <linux@eikelenboom.it>
  31 Acked-by: David Hildenbrand <david@redhat.com>  [core changes]
  32 Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
  33 ---
  34  arch/x86/include/asm/pgtable.h |  8 ++++++++
  35  include/linux/pgtable.h        | 11 +++++++++++
  36  mm/vmscan.c                    | 10 +++++-----
  37  3 files changed, 24 insertions(+), 5 deletions(-)
  38
  39 diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h
  40 index c4b64ee357fd..d8363c676496 100644
  41 --- a/arch/x86/include/asm/pgtable.h
  42 +++ b/arch/x86/include/asm/pgtable.h
  43 @@ -1405,6 +1405,14 @@ static inline bool arch_has_hw_pte_young(void)
  44         return true;
  45  }
  46
  47 +#ifdef CONFIG_XEN_PV
  48 +#define arch_has_hw_nonleaf_pmd_young arch_has_hw_nonleaf_pmd_young
  49 +static inline bool arch_has_hw_nonleaf_pmd_young(void)
  50 +{
  51 +       return !cpu_feature_enabled(X86_FEATURE_XENPV);
  52 +}
  53 +#endif
  54 +
  55  #endif /* __ASSEMBLY__ */
  56
  57  #endif /* _ASM_X86_PGTABLE_H */
  58 diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h
  59 index dec3d890e814..562b4cc82b33 100644
  60 --- a/include/linux/pgtable.h
  61 +++ b/include/linux/pgtable.h
  62 @@ -266,6 +266,17 @@ static inline int pmdp_clear_flush_young(struct vm_area_struct *vma,
  63  #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
  64  #endif
  65
  66 +#ifndef arch_has_hw_nonleaf_pmd_young
  67 +/*
  68 + * Return whether the accessed bit in non-leaf PMD entries is supported on the
  69 + * local CPU.
  70 + */
  71 +static inline bool arch_has_hw_nonleaf_pmd_young(void)
  72 +{
  73 +       return IS_ENABLED(CONFIG_ARCH_HAS_NONLEAF_PMD_YOUNG);
  74 +}
  75 +#endif
  76 +
  77  #ifndef arch_has_hw_pte_young
  78  /*
  79   * Return whether the accessed bit is supported on the local CPU.
  80 diff --git a/mm/vmscan.c b/mm/vmscan.c
  81 index d310e0b9e520..96f1af44bb77 100644
  82 --- a/mm/vmscan.c
  83 +++ b/mm/vmscan.c
  84 @@ -3730,7 +3730,7 @@ static void walk_pmd_range_locked(pud_t *pud, unsigned long next, struct vm_area
  85                         goto next;
  86
  87                 if (!pmd_trans_huge(pmd[i])) {
  88 -                       if (IS_ENABLED(CONFIG_ARCH_HAS_NONLEAF_PMD_YOUNG) &&
  89 +                       if (arch_has_hw_nonleaf_pmd_young() &&
  90                             get_cap(LRU_GEN_NONLEAF_YOUNG))
  91                                 pmdp_test_and_clear_young(vma, addr, pmd + i);
  92                         goto next;
  93 @@ -3828,14 +3828,14 @@ static void walk_pmd_range(pud_t *pud, unsigned long start, unsigned long end,
  94  #endif
  95                 walk->mm_stats[MM_NONLEAF_TOTAL]++;
  96
  97 -#ifdef CONFIG_ARCH_HAS_NONLEAF_PMD_YOUNG
  98 -               if (get_cap(LRU_GEN_NONLEAF_YOUNG)) {
  99 +               if (arch_has_hw_nonleaf_pmd_young() &&
 100 +                   get_cap(LRU_GEN_NONLEAF_YOUNG)) {
 101                         if (!pmd_young(val))
 102                                 continue;
 103
 104                         walk_pmd_range_locked(pud, addr, vma, args, bitmap, &pos);
 105                 }
 106 -#endif
 107 +
 108                 if (!walk->force_scan && !test_bloom_filter(walk->lruvec, walk->max_seq, pmd + i))
 109                         continue;
 110
 111 @@ -5135,7 +5135,7 @@ static ssize_t show_enabled(struct kobject *kobj, struct kobj_attribute *attr, c
 112         if (arch_has_hw_pte_young() && get_cap(LRU_GEN_MM_WALK))
 113                 caps |= BIT(LRU_GEN_MM_WALK);
 114
 115 -       if (IS_ENABLED(CONFIG_ARCH_HAS_NONLEAF_PMD_YOUNG) && get_cap(LRU_GEN_NONLEAF_YOUNG))
 116 +       if (arch_has_hw_nonleaf_pmd_young() && get_cap(LRU_GEN_NONLEAF_YOUNG))
 117                 caps |= BIT(LRU_GEN_NONLEAF_YOUNG);
 118
 119         return snprintf(buf, PAGE_SIZE, "0x%04x\n", caps);
 120 --
 121 2.40.0
 122