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x86/mm: Preallocate all PAE page tables

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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
This commit is contained in:
Dave Hansen 2025-04-14 10:32:41 -07:00
parent 82f120010f
commit 454e65b4fb
1 changed files with 3 additions and 9 deletions
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12
arch/x86/mm/pgtable.c
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@ -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
/*