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s390/pgtable: Fix guest overindication for change bit 

When doing the transition invalid->valid in the host page table for
a guest, then the guest view of C/R is in the pgste. After validation
the view is pgste OR real key. We must zero out the real key C/R to
avoid guest over-indication for change (and reference).

Touching the real key is ok also for the host: The change bit is
tracked via write protection and the reference bit is also ok
because set_pte_at was called and  the page will be touched anyway
soon. Furthermore architecture defines reference as "substantially
accurate", over- and underindication are ok.

Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
This commit is contained in:
Christian Borntraeger 2013-06-04 09:53:59 +02:00 committed by Martin Schwidefsky
parent 4d3797d7e1
commit 338679f7ba
1 changed files with 9 additions and 7 deletions
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16
arch/s390/include/asm/pgtable.h
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@ -704,17 +704,19 @@ static inline void pgste_set_key(pte_t *ptep, pgste_t pgste, pte_t entry)
{
#ifdef CONFIG_PGSTE
unsigned long address;
unsigned long okey, nkey;
unsigned long nkey;
if (pte_val(entry) & _PAGE_INVALID)
return;
VM_BUG_ON(!(pte_val(*ptep) & _PAGE_INVALID));
address = pte_val(entry) & PAGE_MASK;
okey = nkey = page_get_storage_key(address);
nkey &= ~(_PAGE_ACC_BITS | _PAGE_FP_BIT);
/* Set page access key and fetch protection bit from pgste */
nkey |= (pgste_val(pgste) & (RCP_ACC_BITS | RCP_FP_BIT)) >> 56;
if (okey != nkey)
page_set_storage_key(address, nkey, 0);
/*
* Set page access key and fetch protection bit from pgste.
* The guest C/R information is still in the PGSTE, set real
* key C/R to 0.
*/
nkey = (pgste_val(pgste) & (RCP_ACC_BITS | RCP_FP_BIT)) >> 56;
page_set_storage_key(address, nkey, 0);
#endif
}