Commit 1c343f7b authored Jun 13, 2016 by Christian Borntraeger Committed by Martin Schwidefsky Jun 13, 2016

KVM: s390/mm: Fix CMMA reset during reboot



commit 1e133ab2 ("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: 1e133ab2 ("s390/mm: split arch/s390/mm/pgtable.c")
Cc: stable@vger.kernel.org # 4.6+
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

parent 5edb5649

arch/s390/mm/pgtable.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -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));

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