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powerpc/mm: Recompute hash value after a failed update

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If we had secondary hash flag set, we ended up modifying hash value in
the updatepp code path. Hence with a failed updatepp we will be using
a wrong hash value for the following hash insert. Fix this by
recomputing hash before insert.

Without this patch we can end up with using wrong slot number in linux
pte. That can result in us missing an hash pte update or invalidate
which can cause memory corruption or even machine check.

Fixes: 6d492ecc64 ("powerpc/THP: Add code to handle HPTE faults for hugepages")
Cc: stable@vger.kernel.org # v3.11+
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Reviewed-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
This commit is contained in:
Aneesh Kumar K.V 2015-09-15 12:30:08 +05:30 committed by Michael Ellerman
parent 655471f54c
commit 36b35d5d80
1 changed files with 2 additions and 1 deletions
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3
arch/powerpc/mm/hugepage-hash64.c
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@ -85,7 +85,6 @@ int __hash_page_thp(unsigned long ea, unsigned long access, unsigned long vsid,
BUG_ON(index >= 4096);
vpn = hpt_vpn(ea, vsid, ssize);
hash = hpt_hash(vpn, shift, ssize);
hpte_slot_array = get_hpte_slot_array(pmdp);
if (psize == MMU_PAGE_4K) {
/*
@ -101,6 +100,7 @@ int __hash_page_thp(unsigned long ea, unsigned long access, unsigned long vsid,
valid = hpte_valid(hpte_slot_array, index);
if (valid) {
/* update the hpte bits */
hash = hpt_hash(vpn, shift, ssize);
hidx = hpte_hash_index(hpte_slot_array, index);
if (hidx & _PTEIDX_SECONDARY)
hash = ~hash;
@ -126,6 +126,7 @@ int __hash_page_thp(unsigned long ea, unsigned long access, unsigned long vsid,
if (!valid) {
unsigned long hpte_group;
hash = hpt_hash(vpn, shift, ssize);
/* insert new entry */
pa = pmd_pfn(__pmd(old_pmd)) << PAGE_SHIFT;
new_pmd |= _PAGE_HASHPTE;