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| author |   Martin Schwidefsky <schwidefsky@de.ibm.com> | 2013-07-23 22:11:42 +0200 |
|---|---|---|
| committer | Martin Schwidefsky <schwidefsky@de.ibm.com> | 2013-08-29 13:20:11 +0200 |
| commit | 0944fe3f4a323f436180d39402cae7f9c46ead17 (patch) | |
| tree | 7b2ada69ff7e3c1fae20ec0b1dffe5e0d0ec2cc6 /arch/s390/mm/pgtable.c | |
| parent | s390/dasd: fix statistics for recovered requests (diff) | |
| download | linux-dev-0944fe3f4a323f436180d39402cae7f9c46ead17.tar.xz linux-dev-0944fe3f4a323f436180d39402cae7f9c46ead17.zip | |
s390/mm: implement software referenced bits
The last remaining use for the storage key of the s390 architecture
is reference counting. The alternative is to make page table entries
invalid while they are old. On access the fault handler marks the
pte/pmd as young which makes the pte/pmd valid if the access rights
allow read access. The pte/pmd invalidations required for software
managed reference bits cost a bit of performance, on the other hand
the RRBE/RRBM instructions to read and reset the referenced bits are
quite expensive as well.
Reviewed-by: Gerald Schaefer <gerald.schaefer@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Diffstat (limited to 'arch/s390/mm/pgtable.c')
| -rw-r--r-- | arch/s390/mm/pgtable.c | 18 |
1 files changed, 7 insertions, 11 deletions
diff --git a/arch/s390/mm/pgtable.c b/arch/s390/mm/pgtable.c index befaea7003f7..6d16132d0850 100644 --- a/arch/s390/mm/pgtable.c +++ b/arch/s390/mm/pgtable.c @@ -754,7 +754,8 @@ static inline unsigned long *page_table_alloc_pgste(struct mm_struct *mm, atomic_set(&page->_mapcount, 3); table = (unsigned long *) page_to_phys(page); clear_table(table, _PAGE_INVALID, PAGE_SIZE/2); - clear_table(table + PTRS_PER_PTE, 0, PAGE_SIZE/2); + clear_table(table + PTRS_PER_PTE, PGSTE_HR_BIT | PGSTE_HC_BIT, + PAGE_SIZE/2); return table; } @@ -792,26 +793,21 @@ int set_guest_storage_key(struct mm_struct *mm, unsigned long addr, pgste_val(new) |= (key & (_PAGE_CHANGED | _PAGE_REFERENCED)) << 48; pgste_val(new) |= (key & (_PAGE_ACC_BITS | _PAGE_FP_BIT)) << 56; if (!(pte_val(*ptep) & _PAGE_INVALID)) { - unsigned long address, bits; - unsigned char skey; + unsigned long address, bits, skey; address = pte_val(*ptep) & PAGE_MASK; - skey = page_get_storage_key(address); + skey = (unsigned long) page_get_storage_key(address); bits = skey & (_PAGE_CHANGED | _PAGE_REFERENCED); + skey = key & (_PAGE_ACC_BITS | _PAGE_FP_BIT); /* Set storage key ACC and FP */ - page_set_storage_key(address, - (key & (_PAGE_ACC_BITS | _PAGE_FP_BIT)), - !nq); - + page_set_storage_key(address, skey, !nq); /* Merge host changed & referenced into pgste */ pgste_val(new) |= bits << 52; - /* Transfer skey changed & referenced bit to kvm user bits */ - pgste_val(new) |= bits << 45; /* PGSTE_UR_BIT & PGSTE_UC_BIT */ } /* changing the guest storage key is considered a change of the page */ if ((pgste_val(new) ^ pgste_val(old)) & (PGSTE_ACC_BITS | PGSTE_FP_BIT | PGSTE_GR_BIT | PGSTE_GC_BIT)) - pgste_val(new) |= PGSTE_UC_BIT; + pgste_val(new) |= PGSTE_HC_BIT; pgste_set_unlock(ptep, new); pte_unmap_unlock(*ptep, ptl); |