linux-kernel - [PATCH 3.16 212/357] KVM: s390/mm: Fix guest storage key corruption in ptep_set_access

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Date:	Fri,  3 Oct 2014 14:29:58 -0700
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org,
	Christian Borntraeger <borntraeger@...ibm.com>,
	Martin Schwidefsky <schwidefsky@...ibm.com>
Subject: [PATCH 3.16 212/357] KVM: s390/mm: Fix guest storage key corruption in ptep_set_access_flags

3.16-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Christian Borntraeger <borntraeger@...ibm.com>

commit 1951497d90d6754201af3e65241a06f9ef6755cd upstream.

commit 0944fe3f4a32 ("s390/mm: implement software referenced bits")
triggered another paging/storage key corruption. There is an
unhandled invalid->valid pte change where we have to set the real
storage key from the pgste.
When doing paging a guest page might be swapcache or swap and when
faulted in it might be read-only and due to a parallel scan old.
An do_wp_page will make it writeable and young. Due to software
reference tracking this page was invalid and now becomes valid.

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

---
 arch/s390/include/asm/pgtable.h |    1 +
 1 file changed, 1 insertion(+)

--- a/arch/s390/include/asm/pgtable.h
+++ b/arch/s390/include/asm/pgtable.h
@@ -1319,6 +1319,7 @@ static inline int ptep_set_access_flags(
 	ptep_flush_direct(vma->vm_mm, address, ptep);
 
 	if (mm_has_pgste(vma->vm_mm)) {
+		pgste_set_key(ptep, pgste, entry, vma->vm_mm);
 		pgste = pgste_set_pte(ptep, pgste, entry);
 		pgste_set_unlock(ptep, pgste);
 	} else


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