x86/mm: Preallocate all PAE page tables

Finally, move away from having PAE kernels share any PMDs across
processes.

This was already the default on PTI kernels which are  the common
case.

Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Link: https://lore.kernel.org/all/20250414173241.1288CAB4%40davehans-spike.ostc.intel.com

diff --git a/arch/x86/mm/pgtable.c b/arch/x86/mm/pgtable.c
index ca07db510d26d4cca11e4c8a75a5c2f49ae0b582..f4fa8fabf326b952a159119165ef47066626093e 100644 (file)
--- a/arch/x86/mm/pgtable.c
+++ b/arch/x86/mm/pgtable.c
@@ -80,16 +80,11 @@ struct mm_struct *pgd_page_get_mm(struct page *page)
 
 static void pgd_ctor(struct mm_struct *mm, pgd_t *pgd)
 {
-       /* If the pgd points to a shared pagetable level (either the
-          ptes in non-PAE, or shared PMD in PAE), then just copy the
-          references from swapper_pg_dir. */
-       if (CONFIG_PGTABLE_LEVELS == 2 ||
-           (CONFIG_PGTABLE_LEVELS == 3 && SHARED_KERNEL_PMD) ||
-           CONFIG_PGTABLE_LEVELS >= 4) {
+       /* PAE preallocates all its PMDs.  No cloning needed. */
+       if (!IS_ENABLED(CONFIG_X86_PAE))
                clone_pgd_range(pgd + KERNEL_PGD_BOUNDARY,
                                swapper_pg_dir + KERNEL_PGD_BOUNDARY,
                                KERNEL_PGD_PTRS);
-       }
 
        /* List used to sync kernel mapping updates */
        pgd_set_mm(pgd, mm);
@@ -122,8 +117,7 @@ static void pgd_dtor(pgd_t *pgd)
  * all 4 top-level entries are used almost immediately in a
  * new process's life, we just pre-populate them here.
  */
-#define PREALLOCATED_PMDS      (static_cpu_has(X86_FEATURE_PTI) ? \
-                                       PTRS_PER_PGD : KERNEL_PGD_BOUNDARY)
+#define PREALLOCATED_PMDS      PTRS_PER_PGD
 #define MAX_PREALLOCATED_PMDS  PTRS_PER_PGD
 
 /*