diff --git a/arch/s390/include/asm/mmu_context.h b/arch/s390/include/asm/mmu_context.h
index 3763734965e4..248d51cdcad9 100644
--- a/arch/s390/include/asm/mmu_context.h
+++ b/arch/s390/include/asm/mmu_context.h
@@ -42,11 +42,11 @@ static inline int init_new_context(struct task_struct *tsk,
 		 */
 	case 0:
 		/* context created by exec, set asce limit to 4TB */
-		mm->context.asce_limit = STACK_TOP_MAX;
+		mm->context.asce_limit = _REGION2_SIZE;
 		mm->context.asce = __pa(mm->pgd) | _ASCE_TABLE_LENGTH |
 				   _ASCE_USER_BITS | _ASCE_TYPE_REGION3;
 		break;
-	case -PAGE_SIZE:
+	case TASK_SIZE_MAX:
 		/* forked 5-level task, set new asce with new_mm->pgd */
 		mm->context.asce = __pa(mm->pgd) | _ASCE_TABLE_LENGTH |
 			_ASCE_USER_BITS | _ASCE_TYPE_REGION1;
diff --git a/arch/s390/include/asm/processor.h b/arch/s390/include/asm/processor.h
index dee5e57da518..d052adfd53f3 100644
--- a/arch/s390/include/asm/processor.h
+++ b/arch/s390/include/asm/processor.h
@@ -93,15 +93,15 @@ extern void __bpon(void);
  */
 
 #define TASK_SIZE_OF(tsk)	(test_tsk_thread_flag(tsk, TIF_31BIT) ? \
-					(1UL << 31) : -PAGE_SIZE)
+					_REGION3_SIZE : TASK_SIZE_MAX)
 #define TASK_UNMAPPED_BASE	(test_thread_flag(TIF_31BIT) ? \
-					(1UL << 30) : (1UL << 41))
+					(_REGION3_SIZE >> 1) : (_REGION2_SIZE >> 1))
 #define TASK_SIZE		TASK_SIZE_OF(current)
 #define TASK_SIZE_MAX		(-PAGE_SIZE)
 
 #define STACK_TOP		(test_thread_flag(TIF_31BIT) ? \
-					(1UL << 31) : (1UL << 42))
-#define STACK_TOP_MAX		(1UL << 42)
+					_REGION3_SIZE : _REGION2_SIZE)
+#define STACK_TOP_MAX		_REGION2_SIZE
 
 #define HAVE_ARCH_PICK_MMAP_LAYOUT
 
diff --git a/arch/s390/mm/pgalloc.c b/arch/s390/mm/pgalloc.c
index 4630fb7705ca..498c98a312f4 100644
--- a/arch/s390/mm/pgalloc.c
+++ b/arch/s390/mm/pgalloc.c
@@ -121,7 +121,7 @@ int crst_table_upgrade(struct mm_struct *mm, unsigned long end)
 		__pgd = (unsigned long *) mm->pgd;
 		pgd_populate(mm, (pgd_t *) pgd, (p4d_t *) __pgd);
 		mm->pgd = (pgd_t *) pgd;
-		mm->context.asce_limit = -PAGE_SIZE;
+		mm->context.asce_limit = TASK_SIZE_MAX;
 		mm->context.asce = __pa(mm->pgd) | _ASCE_TABLE_LENGTH |
 			_ASCE_USER_BITS | _ASCE_TYPE_REGION1;
 	}
@@ -527,7 +527,7 @@ void base_asce_free(unsigned long asce)
 		base_region2_walk(table, 0, _REGION1_SIZE, 0);
 		break;
 	case _ASCE_TYPE_REGION1:
-		base_region1_walk(table, 0, -_PAGE_SIZE, 0);
+		base_region1_walk(table, 0, TASK_SIZE_MAX, 0);
 		break;
 	}
 	base_crst_free(table);