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KVM: s390/mm: Fix CMMA reset during reboot

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commit 1e133ab296 ("s390/mm: split arch/s390/mm/pgtable.c") factored
out the page table handling code from __gmap_zap and  __s390_reset_cmma
into ptep_zap_unused and added a simple flag that tells which one of the
function (reset or not) is to be made. This also changed the behaviour,
as it also zaps unused page table entries on reset.
Turns out that this is wrong as s390_reset_cmma uses the page walker,
which DOES NOT take the ptl lock.

The most simple fix is to not do the zapping part on reset (which uses
the walker)

Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Fixes: 1e133ab296 ("s390/mm: split arch/s390/mm/pgtable.c")
Cc: stable@vger.kernel.org # 4.6+
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
This commit is contained in:
Christian Borntraeger 2016-06-13 13:14:56 +02:00 committed by Martin Schwidefsky
parent 5edb56491d
commit 1c343f7b0e
1 changed files with 1 additions and 1 deletions
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2
arch/s390/mm/pgtable.c
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@ -437,7 +437,7 @@ void ptep_zap_unused(struct mm_struct *mm, unsigned long addr,
pgste = pgste_get_lock(ptep);
pgstev = pgste_val(pgste);
pte = *ptep;
if (pte_swap(pte) &&
if (!reset && pte_swap(pte) &&
((pgstev & _PGSTE_GPS_USAGE_MASK) == _PGSTE_GPS_USAGE_UNUSED ||
(pgstev & _PGSTE_GPS_ZERO))) {
ptep_zap_swap_entry(mm, pte_to_swp_entry(pte));