[S390] Virtual memmap for s390.

Virtual memmap support for s390. Inspired by the ia64 implementation.

Unlike ia64 we need a mechanism which allows us to dynamically attach
shared memory regions.
These memory regions are accessed via the dcss device driver. dcss
implements the 'direct_access' operation, which requires struct pages
for every single shared page.
Therefore this implementation provides an interface to attach/detach
shared memory:

int add_shared_memory(unsigned long start, unsigned long size);
int remove_shared_memory(unsigned long start, unsigned long size);

The purpose of the add_shared_memory function is to add the given
memory range to the 1:1 mapping and to make sure that the
corresponding range in the vmemmap is backed with physical pages.
It also initialises the new struct pages.

remove_shared_memory in turn only invalidates the page table
entries in the 1:1 mapping. The page tables and the memory used for
struct pages in the vmemmap are currently not freed. They will be
reused when the next segment will be attached.
Given that the maximum size of a shared memory region is 2GB and
in addition all regions must reside below 2GB this is not too much of
a restriction, but there is room for improvement.

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

1 files changed, 12 insertions, 4 deletions

diff --git a/include/asm-s390/pgtable.h b/include/asm-s390/pgtable.h
index 2d968a69ed1..ae61aca5d48 100644
--- a/include/asm-s390/pgtable.h
+++ b/include/asm-s390/pgtable.h
@@ -107,23 +107,25 @@ extern char empty_zero_page[PAGE_SIZE];
  * The vmalloc() routines leaves a hole of 4kB between each vmalloced
  * area for the same reason. ;)
  */
+extern unsigned long vmalloc_end;
 #define VMALLOC_OFFSET  (8*1024*1024)
 #define VMALLOC_START   (((unsigned long) high_memory + VMALLOC_OFFSET) \
 			 & ~(VMALLOC_OFFSET-1))
+#define VMALLOC_END	vmalloc_end
 
 /*
  * We need some free virtual space to be able to do vmalloc.
  * VMALLOC_MIN_SIZE defines the minimum size of the vmalloc
  * area. On a machine with 2GB memory we make sure that we
  * have at least 128MB free space for vmalloc. On a machine
- * with 4TB we make sure we have at least 1GB.
+ * with 4TB we make sure we have at least 128GB.
  */
 #ifndef __s390x__
 #define VMALLOC_MIN_SIZE	0x8000000UL
-#define VMALLOC_END		0x80000000UL
+#define VMALLOC_END_INIT	0x80000000UL
 #else /* __s390x__ */
-#define VMALLOC_MIN_SIZE	0x40000000UL
-#define VMALLOC_END		0x40000000000UL
+#define VMALLOC_MIN_SIZE	0x2000000000UL
+#define VMALLOC_END_INIT	0x40000000000UL
 #endif /* __s390x__ */
 
 /*
@@ -815,11 +817,17 @@ static inline pte_t mk_swap_pte(unsigned long type, unsigned long offset)
 
 #define kern_addr_valid(addr)   (1)
 
+extern int add_shared_memory(unsigned long start, unsigned long size);
+extern int remove_shared_memory(unsigned long start, unsigned long size);
+
 /*
  * No page table caches to initialise
  */
 #define pgtable_cache_init()	do { } while (0)
 
+#define __HAVE_ARCH_MEMMAP_INIT
+extern void memmap_init(unsigned long, int, unsigned long, unsigned long);
+
 #define __HAVE_ARCH_PTEP_ESTABLISH
 #define __HAVE_ARCH_PTEP_SET_ACCESS_FLAGS
 #define __HAVE_ARCH_PTEP_TEST_AND_CLEAR_YOUNG