Commit 1442bb87 authored by Vasily Gorbik's avatar Vasily Gorbik Committed by Heiko Carstens
Browse files

s390/boot: Use entire page for PTEs 



Make boot_pte_alloc() always allocate a full PAGE_SIZE page for
PTE tables, instead of carving two 2K PTE tables out of a single
4K page, similar to commit daa8af80 ("s390/mm: Allocate page
table with PAGE_SIZE granularity").

This mirrors the change in the vmem code and ensures that boot page
tables backing the early KASAN shadow can later be fully freed by
the vmem page-table teardown helpers (e.g. when unmapping early
KASAN shadow on memory hotplug).

The leftover-based allocation was originally added to reduce physmem
allocator fragmentation when EDAT was disabled. On current hardware
EDAT1 is available on all production systems, so the complexity is no
longer justified and gets in the way of freeing the shadow 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 d9f59178

arch/s390/boot/vmem.c

+2 −14
Original line number Diff line number Diff line
@@ -244,22 +244,10 @@ static void *boot_crst_alloc(unsigned long val) 


static pte_t *boot_pte_alloc(void)

{

	static void *pte_leftover;

	pte_t *pte;



	/*

	 * handling pte_leftovers this way helps to avoid memory fragmentation

	 * during POPULATE_KASAN_MAP_SHADOW when EDAT is off

	 */

	if (!pte_leftover) {

		pte_leftover = (void *)physmem_alloc_or_die(RR_VMEM, PAGE_SIZE, PAGE_SIZE);

		pte = pte_leftover + _PAGE_TABLE_SIZE;

	pte = (void *)physmem_alloc_or_die(RR_VMEM, PAGE_SIZE, PAGE_SIZE);

	__arch_set_page_dat(pte, 1);

	} else {

		pte = pte_leftover;

		pte_leftover = NULL;

	}



	memset64((u64 *)pte, _PAGE_INVALID, PTRS_PER_PTE);

	return pte;

}