[S390] dynamic page tables.

Add support for different number of page table levels dependent
on the highest address used for a process. This will cause a 31 bit
process to use a two level page table instead of the four level page
table that is the default after the pud has been introduced. Likewise
a normal 64 bit process will use three levels instead of four. Only
if a process runs out of the 4 tera bytes which can be addressed with
a three level page table the fourth level is dynamically added. Then
the process can use up to 8 peta byte.

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

1 files changed, 3 insertions, 22 deletions

diff --git a/include/asm-s390/processor.h b/include/asm-s390/processor.h
index 5a21f457d583..51d88912aa20 100644
--- a/include/asm-s390/processor.h
+++ b/include/asm-s390/processor.h
@@ -81,11 +81,12 @@ extern int get_cpu_capability(unsigned int *);
 
 #ifndef __s390x__
 #define STACK_TOP               (1UL << 31)
+#define STACK_TOP_MAX           (1UL << 31)
 #else /* __s390x__ */
-#define STACK_TOP               (1UL << (test_thread_flag(TIF_31BIT) ? 31:53))
+#define STACK_TOP               (1UL << (test_thread_flag(TIF_31BIT) ? 31:42))
+#define STACK_TOP_MAX           (1UL << 42)
 #endif /* __s390x__ */
 
-#define STACK_TOP_MAX           STACK_TOP
 
 #endif
 
@@ -142,8 +143,6 @@ struct stack_frame {
 /*
  * Do necessary setup to start up a new thread.
  */
-#ifndef __s390x__
-
 #define start_thread(regs, new_psw, new_stackp) do {            \
         set_fs(USER_DS);                                        \
         regs->psw.mask  = psw_user_bits;                        \
@@ -151,24 +150,6 @@ struct stack_frame {
         regs->gprs[15]  = new_stackp ;                          \
 } while (0)
 
-#else /* __s390x__ */
-
-#define start_thread(regs, new_psw, new_stackp) do {            \
-        set_fs(USER_DS);                                        \
-        regs->psw.mask  = psw_user_bits;                        \
-        regs->psw.addr  = new_psw;                              \
-        regs->gprs[15]  = new_stackp;                           \
-} while (0)
-
-#define start_thread31(regs, new_psw, new_stackp) do {          \
-        set_fs(USER_DS);                                        \
-        regs->psw.mask  = psw_user32_bits;                      \
-        regs->psw.addr  = new_psw;                              \
-        regs->gprs[15]  = new_stackp;                           \
-} while (0)
-
-#endif /* __s390x__ */
-
 /* Forward declaration, a strange C thing */
 struct task_struct;
 struct mm_struct;