s390/cmma: rework no-dat handling

Rework the way physical pages are set no-dat / dat:

The old way is:

- Rely on that all pages are initially marked "dat"
- Allocate page tables for the kernel mapping
- Enable dat
- Walk the whole kernel mapping and set PG_arch_1 bit in all struct pages
  that belong to pages of kernel page tables
- Walk all struct pages and test and clear the PG_arch_1 bit. If the bit is
  not set, set the page state to no-dat
- For all subsequent page table allocations, set the page state to dat
  (remove the no-dat state) on allocation time

Change this rather complex logic to a simpler approach:

- Set the whole physical memory (all pages) to "no-dat"
- Explicitly set those page table pages to "dat" which are part of the
  kernel image (e.g. swapper_pg_dir)
- For all subsequent page table allocations, set the page state to dat
  (remove the no-dat state) on allocation time

In result the code is simpler, and this also allows to get rid of one
odd usage of the PG_arch_1 bit.

Reviewed-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>

1 files changed, 2 insertions, 2 deletions

diff --git a/arch/s390/mm/vmem.c b/arch/s390/mm/vmem.c
index b13990776fae..186a020857cf 100644
--- a/arch/s390/mm/vmem.c
+++ b/arch/s390/mm/vmem.c
@@ -50,8 +50,7 @@ void *vmem_crst_alloc(unsigned long val)
 	if (!table)
 		return NULL;
 	crst_table_init(table, val);
-	if (slab_is_available())
-		__arch_set_page_dat(table, 1UL << CRST_ALLOC_ORDER);
+	__arch_set_page_dat(table, 1UL << CRST_ALLOC_ORDER);
 	return table;
 }
 
@@ -67,6 +66,7 @@ pte_t __ref *vmem_pte_alloc(void)
 	if (!pte)
 		return NULL;
 	memset64((u64 *)pte, _PAGE_INVALID, PTRS_PER_PTE);
+	__arch_set_page_dat(pte, 1);
 	return pte;
 }