From: Heiko Carstens <heiko.carstens@de.ibm.com>

Introduce ARCH_LOW_ADDRESS_LIMIT which can be set per architecture to
override the 4GB default limit used by the bootmem allocater within
__alloc_bootmem_low() and __alloc_bootmem_low_node().  E.g.  s390 needs a
2GB limit instead of 4GB.

Acked-by: Ingo Molnar <mingo@elte.hu>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
---

 include/asm-s390/processor.h |    2 ++
 mm/bootmem.c                 |   11 ++++++++---
 2 files changed, 10 insertions(+), 3 deletions(-)

diff -puN include/asm-s390/processor.h~bootmem-use-max_dma_address-instead-of-low32limit include/asm-s390/processor.h
--- a/include/asm-s390/processor.h~bootmem-use-max_dma_address-instead-of-low32limit
+++ a/include/asm-s390/processor.h
@@ -337,6 +337,8 @@ struct notifier_block;
 int register_idle_notifier(struct notifier_block *nb);
 int unregister_idle_notifier(struct notifier_block *nb);
 
+#define ARCH_LOW_ADDRESS_LIMIT	0x7fffffffUL
+
 #endif
 
 #endif                                 /* __ASM_S390_PROCESSOR_H           */
diff -puN mm/bootmem.c~bootmem-use-max_dma_address-instead-of-low32limit mm/bootmem.c
--- a/mm/bootmem.c~bootmem-use-max_dma_address-instead-of-low32limit
+++ a/mm/bootmem.c
@@ -15,6 +15,7 @@
 
 #include <asm/bug.h>
 #include <asm/io.h>
+#include <asm/processor.h>
 
 #include "internal.h"
 
@@ -453,7 +454,9 @@ void * __init __alloc_bootmem_node(pg_da
 	return __alloc_bootmem(size, align, goal);
 }
 
-#define LOW32LIMIT 0xffffffff
+#ifndef ARCH_LOW_ADDRESS_LIMIT
+#define ARCH_LOW_ADDRESS_LIMIT	0xffffffffUL
+#endif
 
 void * __init __alloc_bootmem_low(unsigned long size, unsigned long align,
 				  unsigned long goal)
@@ -462,7 +465,8 @@ void * __init __alloc_bootmem_low(unsign
 	void *ptr;
 
 	list_for_each_entry(bdata, &bdata_list, list) {
-		ptr = __alloc_bootmem_core(bdata, size, align, goal, LOW32LIMIT);
+		ptr = __alloc_bootmem_core(bdata, size, align, goal,
+						ARCH_LOW_ADDRESS_LIMIT);
 		if (ptr)
 			return ptr;
 	}
@@ -478,5 +482,6 @@ void * __init __alloc_bootmem_low(unsign
 void * __init __alloc_bootmem_low_node(pg_data_t *pgdat, unsigned long size,
 				       unsigned long align, unsigned long goal)
 {
-	return __alloc_bootmem_core(pgdat->bdata, size, align, goal, LOW32LIMIT);
+	return __alloc_bootmem_core(pgdat->bdata, size, align, goal,
+				    ARCH_LOW_ADDRESS_LIMIT);
 }
_