Commit 6a35d02f authored by Vasily Gorbik's avatar Vasily Gorbik Committed by Heiko Carstens
Browse files

s390/vmem: Support 2G page splitting for KASAN shadow freeing 



Export split_pud_page() so it can be used from the vmem code and teach
modify_pud_table() to split PUD-sized mappings when only a subrange
needs to be removed.

If the range to be removed covers a full PUD-sized mapping, keep the
existing behavior: clear the PUD entry and free the backing large page
(for non-direct mappings). Otherwise, split the PUD-mapped page into
PMD mappings and let the walker handle the smaller ranges.

This is needed for KASAN early shadow removal support: memory hotplug
freeing the KASAN early shadow is the only expected caller that will
try to free 2G PUD-mapped regions of non-direct mappings.

Signed-off-by: default avatarVasily Gorbik <gor@linux.ibm.com>
Reviewed-by: default avatarHeiko Carstens <hca@linux.ibm.com>
Signed-off-by: default avatarHeiko Carstens <hca@linux.ibm.com>
parent 1442bb87

arch/s390/include/asm/page.h

+2 −0
Original line number Diff line number Diff line
@@ -166,6 +166,8 @@ static inline int page_reset_referenced(unsigned long addr) 
	return CC_TRANSFORM(cc);

}



int split_pud_page(pud_t *pudp, unsigned long addr);



/* Bits int the storage key */

#define _PAGE_CHANGED		0x02	/* HW changed bit		*/

#define _PAGE_REFERENCED	0x04	/* HW referenced bit		*/

arch/s390/mm/pageattr.c

+1 −1
Original line number Diff line number Diff line
@@ -204,7 +204,7 @@ static int walk_pmd_level(pud_t *pudp, unsigned long addr, unsigned long end, 
	return rc;

}



static int split_pud_page(pud_t *pudp, unsigned long addr)

int split_pud_page(pud_t *pudp, unsigned long addr)

{

	unsigned long pmd_addr, prot;

	pmd_t *pm_dir, *pmdp;

arch/s390/mm/vmem.c

+5 −1
Original line number Diff line number Diff line
@@ -330,10 +330,14 @@ static int modify_pud_table(p4d_t *p4d, unsigned long addr, unsigned long end, 
			if (pud_leaf(*pud)) {

				if (IS_ALIGNED(addr, PUD_SIZE) &&

				    IS_ALIGNED(next, PUD_SIZE)) {

					if (!direct)

						vmem_free_pages(pud_deref(*pud), get_order(PUD_SIZE), altmap);

					pud_clear(pud);

					pages++;

				}

					continue;

				} else {

					split_pud_page(pud, addr & PUD_MASK);

				}

			}

		} else if (pud_none(*pud)) {

			if (IS_ALIGNED(addr, PUD_SIZE) &&