[S390] store indication fault optimization
Use the store indication bit in the translation exception code on
page faults to avoid the protection faults that immediatly follow
the page fault if the access has been a write.
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
diff --git a/arch/s390/mm/fault.c b/arch/s390/mm/fault.c
index 2505b2e..b49d120 100644
--- a/arch/s390/mm/fault.c
+++ b/arch/s390/mm/fault.c
@@ -52,6 +52,19 @@
#define VM_FAULT_BADMAP 0x020000
#define VM_FAULT_BADACCESS 0x040000
+static unsigned long store_indication;
+
+void fault_init(void)
+{
+ unsigned long long facility_list[2];
+
+ if (stfle(facility_list, 2) < 2)
+ return;
+ if ((facility_list[0] & (1ULL << 61)) &&
+ (facility_list[1] & (1ULL << 52)))
+ store_indication = 0xc00;
+}
+
static inline int notify_page_fault(struct pt_regs *regs)
{
int ret = 0;
@@ -294,7 +307,7 @@
struct mm_struct *mm;
struct vm_area_struct *vma;
unsigned long address;
- int fault;
+ int fault, write;
if (notify_page_fault(regs))
return 0;
@@ -348,8 +361,10 @@
* make sure we exit gracefully rather than endlessly redo
* the fault.
*/
- fault = handle_mm_fault(mm, vma, address,
- (access == VM_WRITE) ? FAULT_FLAG_WRITE : 0);
+ write = (access == VM_WRITE ||
+ (trans_exc_code & store_indication) == 0x400) ?
+ FAULT_FLAG_WRITE : 0;
+ fault = handle_mm_fault(mm, vma, address, write);
if (unlikely(fault & VM_FAULT_ERROR))
goto out_up;