s390/mm: fix CMMA vs KSM vs others

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commit a8f60d1fad upstream.

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.

Signed-of-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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Christian Borntraeger 2017-04-09 22:09:38 +02:00 • committed by Greg Kroah-Hartman

parent f79ef57911

commit 3d42ca46f4

1 changed files with 2 additions and 0 deletions

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arch/s390/include/asm/pgtable.h

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