Commit 454e65b4 authored by Dave Hansen's avatar Dave Hansen
Browse files

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: default avatarDave Hansen <dave.hansen@linux.intel.com>
Link: https://lore.kernel.org/all/20250414173241.1288CAB4%40davehans-spike.ostc.intel.com
parent 82f12001

arch/x86/mm/pgtable.c

+3 −9
Original line number Diff line number Diff line
@@ -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



/*