s390: make MAX_PHYSMEM_BITS configurable

Signed-off-by: NHeiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: NMartin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/Kconfig

@@ -537,6 +537,16 @@ config FORCE_MAX_ZONEORDER
 
 source "mm/Kconfig"
 
+config MAX_PHYSMEM_BITS
+	int "Maximum size of supported physical memory in bits (42-53)"
+	range 42 53
+	default "46"
+	help
+	  This option specifies the maximum supported size of physical memory
+	  in bits. Supported is any size between 2^42 (4TB) and 2^53 (8PB).
+	  Increasing the number of bits also increases the kernel image size.
+	  By default 46 bits (64TB) are supported.
+
 config PACK_STACK
 	def_bool y
 	prompt "Pack kernel stack"

arch/s390/include/asm/sparsemem.h

@@ -2,6 +2,6 @@
 #define _ASM_S390_SPARSEMEM_H
 
 #define SECTION_SIZE_BITS	28
-#define MAX_PHYSMEM_BITS	46
+#define MAX_PHYSMEM_BITS	CONFIG_MAX_PHYSMEM_BITS
 
 #endif /* _ASM_S390_SPARSEMEM_H */