Commit 396f0fe4 authored by Christian Borntraeger's avatar Christian Borntraeger Committed by Sasha Levin

s390/mm: fix CMMA vs KSM vs others

[ Upstream commit a8f60d1f ]

On heavy paging with KSM I see guest data corruption. Turns out that
KSM will add pages to its tree, where the mapping return true for
pte_unused (or might become as such later).  KSM will unmap such pages
and reinstantiate with different attributes (e.g. write protected or
special, e.g. in replace_page or write_protect_page)). This uncovered
a bug in our pagetable handling: We must remove the unused flag as
soon as an entry becomes present again.

Cc: stable@vger.kernel.org
Signed-of-by: default avatarChristian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: default avatarMartin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: default avatarSasha Levin <alexander.levin@verizon.com>
parent fab0b034
...@@ -767,6 +767,8 @@ static inline void set_pte_at(struct mm_struct *mm, unsigned long addr, ...@@ -767,6 +767,8 @@ static inline void set_pte_at(struct mm_struct *mm, unsigned long addr,
{ {
pgste_t pgste; pgste_t pgste;
if (pte_present(entry))
pte_val(entry) &= ~_PAGE_UNUSED;
if (mm_has_pgste(mm)) { if (mm_has_pgste(mm)) {
pgste = pgste_get_lock(ptep); pgste = pgste_get_lock(ptep);
pgste_val(pgste) &= ~_PGSTE_GPS_ZERO; pgste_val(pgste) &= ~_PGSTE_GPS_ZERO;
......
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