[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>
This commit is contained in:
Martin Schwidefsky 2010-10-25 16:10:13 +02:00 committed by Martin Schwidefsky
parent 6931be0803
commit 92f842eac7
3 changed files with 20 additions and 3 deletions

View File

@ -38,6 +38,7 @@
extern pgd_t swapper_pg_dir[] __attribute__ ((aligned (4096)));
extern void paging_init(void);
extern void vmem_map_init(void);
extern void fault_init(void);
/*
* The S390 doesn't have any external MMU info: the kernel page

View File

@ -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 @@ static inline int do_exception(struct pt_regs *regs, int access,
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 @@ static inline int do_exception(struct pt_regs *regs, int access,
* 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;

View File

@ -124,6 +124,7 @@ void __init paging_init(void)
#endif
max_zone_pfns[ZONE_NORMAL] = max_low_pfn;
free_area_init_nodes(max_zone_pfns);
fault_init();
}
void __init mem_init(void)