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[S390] store indication fault optimization

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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
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1
arch/s390/include/asm/pgtable.h
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

21
arch/s390/mm/fault.c
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;

1
arch/s390/mm/init.c
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)