Commit b0cc4d19 authored by Dave Hansen's avatar Dave Hansen
Browse files

x86/mm: Always "broadcast" PMD setting operations 



Kernel PMDs can either be shared across processes or private to a
process.  On 64-bit, they are always shared.  32-bit non-PAE hardware
does not have PMDs, but the kernel logically squishes them into the
PGD and treats them as private. Here are the four cases:

	64-bit:                Shared
	32-bit: non-PAE:       Private
	32-bit:     PAE+  PTI: Private
	32-bit:     PAE+noPTI: Shared

Note that 32-bit is all "Private" except for PAE+noPTI being an
oddball.  The 32-bit+PAE+noPTI case will be made like the rest of
32-bit shortly.

But until that can be done, temporarily treat the 32-bit+PAE+noPTI
case as Private. This will do unnecessary walks across pgd_list and
unnecessary PTE setting but should be otherwise harmless.

Signed-off-by: default avatarDave Hansen <dave.hansen@linux.intel.com>
Link: https://lore.kernel.org/all/20250414173235.F63F50D1%40davehans-spike.ostc.intel.com
parent 780f97e3

arch/x86/mm/pat/set_memory.c

+2 −2
Original line number Diff line number Diff line
@@ -889,7 +889,7 @@ static void __set_pmd_pte(pte_t *kpte, unsigned long address, pte_t pte) 
	/* change init_mm */

	set_pte_atomic(kpte, pte);

#ifdef CONFIG_X86_32

	if (!SHARED_KERNEL_PMD) {

	{

		struct page *page;



		list_for_each_entry(page, &pgd_list, lru) {
@@ -1293,7 +1293,7 @@ static int collapse_pmd_page(pmd_t *pmd, unsigned long addr, 
	/* Queue the page table to be freed after TLB flush */

	list_add(&page_ptdesc(pmd_page(old_pmd))->pt_list, pgtables);



	if (IS_ENABLED(CONFIG_X86_32) && !SHARED_KERNEL_PMD) {

	if (IS_ENABLED(CONFIG_X86_32)) {

		struct page *page;



		/* Update all PGD tables to use the same large page */

arch/x86/mm/pgtable.c

+3 −8
Original line number Diff line number Diff line
@@ -97,18 +97,13 @@ static void pgd_ctor(struct mm_struct *mm, pgd_t *pgd) 
				KERNEL_PGD_PTRS);

	}



	/* list required to sync kernel mapping updates */

	if (!SHARED_KERNEL_PMD) {

	/* List used to sync kernel mapping updates */

	pgd_set_mm(pgd, mm);

	pgd_list_add(pgd);

}

}



static void pgd_dtor(pgd_t *pgd)

{

	if (SHARED_KERNEL_PMD)

		return;



	spin_lock(&pgd_lock);

	pgd_list_del(pgd);

	spin_unlock(&pgd_lock);