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Commit 338679f7 authored by Christian Borntraeger's avatar Christian Borntraeger Committed by Martin Schwidefsky
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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: default avatarChristian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: default avatarMartin Schwidefsky <schwidefsky@de.ibm.com>
parent 4d3797d7

arch/s390/include/asm/pgtable.h

+9 −7
Original line number Diff line number Diff line
@@ -704,16 +704,18 @@ 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)

	/*

	 * 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

}