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s390/mm,kvm: fix software dirty bits vs. kvm for old machines

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For machines without enhanced supression on protection the software
dirty bit code forces the pte dirty bit and clears the page protection
bit in pgste_set_pte. This is done for all pte types, the check for
present ptes is missing. As a result swap ptes and other not-present
ptes can get corrupted.
Add a check for the _PAGE_PRESENT bit to pgste_set_pte before modifying
the pte value.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
This commit is contained in:
Martin Schwidefsky 2013-10-07 16:15:29 +02:00
parent 1e52db6908
commit af0ebc40a8
1 changed files with 3 additions and 1 deletions
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4
arch/s390/include/asm/pgtable.h
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@ -748,7 +748,9 @@ static inline void pgste_set_key(pte_t *ptep, pgste_t pgste, pte_t entry)
static inline void pgste_set_pte(pte_t *ptep, pte_t entry)
{
if (!MACHINE_HAS_ESOP && (pte_val(entry) & _PAGE_WRITE)) {
if (!MACHINE_HAS_ESOP &&
(pte_val(entry) & _PAGE_PRESENT) &&
(pte_val(entry) & _PAGE_WRITE)) {
/*
* Without enhanced suppression-on-protection force
* the dirty bit on for all writable ptes.