[S390] add support for physical memory > 4TB

The kernel address space of a 64 bit kernel currently uses a three level
page table and the vmemmap array has a fixed address and a fixed maximum
size. A three level page table is good enough for systems with less than
3.8TB of memory, for bigger systems four page table levels need to be
used. Each page table level costs a bit of performance, use 3 levels for
normal systems and 4 levels only for the really big systems.
To avoid bloating sparse.o too much set MAX_PHYSMEM_BITS to 46 for a
maximum of 64TB of memory.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

2 files changed, 5 insertions, 22 deletions

diff --git a/arch/s390/include/asm/pgtable.h b/arch/s390/include/asm/pgtable.h
index 4f289ff..011358c 100644
--- a/arch/s390/include/asm/pgtable.h
+++ b/arch/s390/include/asm/pgtable.h
@@ -128,28 +128,11 @@ static inline int is_zero_pfn(unsigned long pfn)
  * effect, this also makes sure that 64 bit module code cannot be used
  * as system call address.
  */
-
 extern unsigned long VMALLOC_START;
+extern unsigned long VMALLOC_END;
+extern struct page *vmemmap;
 
-#ifndef __s390x__
-#define VMALLOC_SIZE	(96UL << 20)
-#define VMALLOC_END	0x7e000000UL
-#define VMEM_MAP_END	0x80000000UL
-#else /* __s390x__ */
-#define VMALLOC_SIZE	(128UL << 30)
-#define VMALLOC_END	0x3e000000000UL
-#define VMEM_MAP_END	0x40000000000UL
-#endif /* __s390x__ */
-
-/*
- * VMEM_MAX_PHYS is the highest physical address that can be added to the 1:1
- * mapping. This needs to be calculated at compile time since the size of the
- * VMEM_MAP is static but the size of struct page can change.
- */
-#define VMEM_MAX_PAGES	((VMEM_MAP_END - VMALLOC_END) / sizeof(struct page))
-#define VMEM_MAX_PFN	min(VMALLOC_START >> PAGE_SHIFT, VMEM_MAX_PAGES)
-#define VMEM_MAX_PHYS	((VMEM_MAX_PFN << PAGE_SHIFT) & ~((16 << 20) - 1))
-#define vmemmap		((struct page *) VMALLOC_END)
+#define VMEM_MAX_PHYS ((unsigned long) vmemmap)
 
 /*
  * A 31 bit pagetable entry of S390 has following format:
diff --git a/arch/s390/include/asm/sparsemem.h b/arch/s390/include/asm/sparsemem.h
index 545d219..0fb3402 100644
--- a/arch/s390/include/asm/sparsemem.h
+++ b/arch/s390/include/asm/sparsemem.h
@@ -4,8 +4,8 @@
 #ifdef CONFIG_64BIT
 
 #define SECTION_SIZE_BITS	28
-#define MAX_PHYSADDR_BITS	42
-#define MAX_PHYSMEM_BITS	42
+#define MAX_PHYSADDR_BITS	46
+#define MAX_PHYSMEM_BITS	46
 
 #else