s390/boot: always align vmalloc area on segment boundary

The size of vmalloc area depends from various factors
on boot and could be set to:

1. Default size as determined by VMALLOC_DEFAULT_SIZE macro;
2. One half of the virtual address space not occupied by
   modules and fixed mappings;
3. The size provided by user with vmalloc= kernel command
   line parameter;

In cases [1] and [2] the vmalloc area base address is aligned
on Region3 table type boundary, while in case [3] in might get
aligned on page boundary.

Limit the waste of page tables and always align vmalloc area
size and base address on segment boundary.
Acked-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Alexander Gordeev <agordeev@linux.ibm.com>

arch/s390/boot/ipl_parm.c

@@ -274,7 +274,7 @@ void parse_boot_command_line(void)
 			memory_limit = round_down(memparse(val, NULL), PAGE_SIZE);
 
 		if (!strcmp(param, "vmalloc") && val) {
-			vmalloc_size = round_up(memparse(val, NULL), PAGE_SIZE);
+			vmalloc_size = round_up(memparse(val, NULL), _SEGMENT_SIZE);
 			vmalloc_size_set = 1;
 		}
 

arch/s390/boot/startup.c

@@ -255,7 +255,8 @@ static unsigned long setup_kernel_memory_layout(void)
 	VMALLOC_END = MODULES_VADDR;
 
 	/* allow vmalloc area to occupy up to about 1/2 of the rest virtual space left */
-	vmalloc_size = min(vmalloc_size, round_down(VMALLOC_END / 2, _REGION3_SIZE));
+	vsize = round_down(VMALLOC_END / 2, _SEGMENT_SIZE);
+	vmalloc_size = min(vmalloc_size, vsize);
 	VMALLOC_START = VMALLOC_END - vmalloc_size;
 
 	/* split remaining virtual space between 1:1 mapping & vmemmap array */