Revert "x86/mm/ident_map: Use gbpages only where full GB page should be mapped."

This reverts commit d794734c9bbfe22f86686dc2909c25f5ffe1a572.

While the original change tries to fix a bug, it also unintentionally broke
existing systems, see the regressions reported at:

  https://lore.kernel.org/all/3a1b9909-45ac-4f97-ad68-d16ef1ce99db@pavinjoseph.com/

Since d794734c9bbf was also marked for -stable, let's back it out before
causing more damage.

Note that due to another upstream change the revert was not 100% automatic:

  0a845e0f6348 mm/treewide: replace pud_large() with pud_leaf()

Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: <stable@vger.kernel.org>
Cc: Russ Anderson <rja@hpe.com>
Cc: Steve Wahl <steve.wahl@hpe.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Link: https://lore.kernel.org/all/3a1b9909-45ac-4f97-ad68-d16ef1ce99db@pavinjoseph.com/
Fixes: d794734c9bbf ("x86/mm/ident_map: Use gbpages only where full GB page should be mapped.")

diff --git a/arch/x86/mm/ident_map.c b/arch/x86/mm/ident_map.c
index a204a332c71fc50948c884251cc15cc89afeaf1f..968d7005f4a72454ccf8678967f040fe06f36ad6 100644 (file)
--- a/arch/x86/mm/ident_map.c
+++ b/arch/x86/mm/ident_map.c
@@ -26,31 +26,18 @@ static int ident_pud_init(struct x86_mapping_info *info, pud_t *pud_page,
        for (; addr < end; addr = next) {
                pud_t *pud = pud_page + pud_index(addr);
                pmd_t *pmd;
-               bool use_gbpage;
 
                next = (addr & PUD_MASK) + PUD_SIZE;
                if (next > end)
                        next = end;
 
-               /* if this is already a gbpage, this portion is already mapped */
-               if (pud_leaf(*pud))
-                       continue;
-
-               /* Is using a gbpage allowed? */
-               use_gbpage = info->direct_gbpages;
-
-               /* Don't use gbpage if it maps more than the requested region. */
-               /* at the begining: */
-               use_gbpage &= ((addr & ~PUD_MASK) == 0);
-               /* ... or at the end: */
-               use_gbpage &= ((next & ~PUD_MASK) == 0);
-
-               /* Never overwrite existing mappings */
-               use_gbpage &= !pud_present(*pud);
-
-               if (use_gbpage) {
+               if (info->direct_gbpages) {
                        pud_t pudval;
 
+                       if (pud_present(*pud))
+                               continue;
+
+                       addr &= PUD_MASK;
                        pudval = __pud((addr - info->offset) | info->page_flag);
                        set_pud(pud, pudval);
                        continue;