queue-6.6/revert-x86-mm-ident_map-use-gbpages-only-where-full-.patch

   1 From 903e6b636ff957419a5c19368ffc685536b7c3b6 Mon Sep 17 00:00:00 2001
   2 From: Sasha Levin <sashal@kernel.org>
   3 Date: Mon, 25 Mar 2024 11:47:51 +0100
   4 Subject: Revert "x86/mm/ident_map: Use gbpages only where full GB page should
   5  be mapped."
   6
   7 From: Ingo Molnar <mingo@kernel.org>
   8
   9 [ Upstream commit c567f2948f57bdc03ed03403ae0234085f376b7d ]
  10
  11 This reverts commit d794734c9bbfe22f86686dc2909c25f5ffe1a572.
  12
  13 While the original change tries to fix a bug, it also unintentionally broke
  14 existing systems, see the regressions reported at:
  15
  16   https://lore.kernel.org/all/3a1b9909-45ac-4f97-ad68-d16ef1ce99db@pavinjoseph.com/
  17
  18 Since d794734c9bbf was also marked for -stable, let's back it out before
  19 causing more damage.
  20
  21 Note that due to another upstream change the revert was not 100% automatic:
  22
  23   0a845e0f6348 mm/treewide: replace pud_large() with pud_leaf()
  24
  25 Signed-off-by: Ingo Molnar <mingo@kernel.org>
  26 Cc: <stable@vger.kernel.org>
  27 Cc: Russ Anderson <rja@hpe.com>
  28 Cc: Steve Wahl <steve.wahl@hpe.com>
  29 Cc: Dave Hansen <dave.hansen@linux.intel.com>
  30 Link: https://lore.kernel.org/all/3a1b9909-45ac-4f97-ad68-d16ef1ce99db@pavinjoseph.com/
  31 Fixes: d794734c9bbf ("x86/mm/ident_map: Use gbpages only where full GB page should be mapped.")
  32 Signed-off-by: Sasha Levin <sashal@kernel.org>
  33 ---
  34  arch/x86/mm/ident_map.c | 23 +++++------------------
  35  1 file changed, 5 insertions(+), 18 deletions(-)
  36
  37 diff --git a/arch/x86/mm/ident_map.c b/arch/x86/mm/ident_map.c
  38 index a204a332c71fc..968d7005f4a72 100644
  39 --- a/arch/x86/mm/ident_map.c
  40 +++ b/arch/x86/mm/ident_map.c
  41 @@ -26,31 +26,18 @@ static int ident_pud_init(struct x86_mapping_info *info, pud_t *pud_page,
  42         for (; addr < end; addr = next) {
  43                 pud_t *pud = pud_page + pud_index(addr);
  44                 pmd_t *pmd;
  45 -               bool use_gbpage;
  46
  47                 next = (addr & PUD_MASK) + PUD_SIZE;
  48                 if (next > end)
  49                         next = end;
  50
  51 -               /* if this is already a gbpage, this portion is already mapped */
  52 -               if (pud_leaf(*pud))
  53 -                       continue;
  54 -
  55 -               /* Is using a gbpage allowed? */
  56 -               use_gbpage = info->direct_gbpages;
  57 -
  58 -               /* Don't use gbpage if it maps more than the requested region. */
  59 -               /* at the begining: */
  60 -               use_gbpage &= ((addr & ~PUD_MASK) == 0);
  61 -               /* ... or at the end: */
  62 -               use_gbpage &= ((next & ~PUD_MASK) == 0);
  63 -
  64 -               /* Never overwrite existing mappings */
  65 -               use_gbpage &= !pud_present(*pud);
  66 -
  67 -               if (use_gbpage) {
  68 +               if (info->direct_gbpages) {
  69                         pud_t pudval;
  70
  71 +                       if (pud_present(*pud))
  72 +                               continue;
  73 +
  74 +                       addr &= PUD_MASK;
  75                         pudval = __pud((addr - info->offset) | info->page_flag);
  76                         set_pud(pud, pudval);
  77                         continue;
  78 --
  79 2.43.0
  80