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Commit 593befa6 authored by Dominik Dingel's avatar Dominik Dingel Committed by Martin Schwidefsky
Browse files

mm: introduce mm_forbids_zeropage function 



Add a new function stub to allow architectures to disable for
an mm_structthe backing of non-present, anonymous pages with
read-only empty zero pages.

Signed-off-by: default avatarDominik Dingel <dingel@linux.vnet.ibm.com>
Reviewed-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
Signed-off-by: default avatarMartin Schwidefsky <schwidefsky@de.ibm.com>
parent a13cff31

include/linux/mm.h

+11 −0
Original line number Diff line number Diff line
@@ -56,6 +56,17 @@ extern int sysctl_legacy_va_layout; 
#define __pa_symbol(x)  __pa(RELOC_HIDE((unsigned long)(x), 0))

#endif



/*

 * To prevent common memory management code establishing

 * a zero page mapping on a read fault.

 * This macro should be defined within <asm/pgtable.h>.

 * s390 does this to prevent multiplexing of hardware bits

 * related to the physical page in case of virtualization.

 */

#ifndef mm_forbids_zeropage

#define mm_forbids_zeropage(X)	(0)

#endif



extern unsigned long sysctl_user_reserve_kbytes;

extern unsigned long sysctl_admin_reserve_kbytes;

mm/huge_memory.c

+1 −1
Original line number Diff line number Diff line
@@ -805,7 +805,7 @@ int do_huge_pmd_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma, 
		return VM_FAULT_OOM;

	if (unlikely(khugepaged_enter(vma)))

		return VM_FAULT_OOM;

	if (!(flags & FAULT_FLAG_WRITE) &&

	if (!(flags & FAULT_FLAG_WRITE) && !mm_forbids_zeropage(mm) &&

			transparent_hugepage_use_zero_page()) {

		spinlock_t *ptl;

		pgtable_t pgtable;

mm/memory.c

+1 −1
Original line number Diff line number Diff line
@@ -2640,7 +2640,7 @@ static int do_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma, 
		return VM_FAULT_SIGBUS;



	/* Use the zero-page for reads */

	if (!(flags & FAULT_FLAG_WRITE)) {

	if (!(flags & FAULT_FLAG_WRITE) && !mm_forbids_zeropage(mm)) {

		entry = pte_mkspecial(pfn_pte(my_zero_pfn(address),

						vma->vm_page_prot));

		page_table = pte_offset_map_lock(mm, pmd, address, &ptl);