[PATCH 1/2] powerpc/mm: Fix crashes with PUD level hugetlb config

[Ram Pai]

On Thu, Feb 08, 2018 at 08:46:27PM +0530, Aneesh Kumar K.V wrote:
> "Aneesh Kumar K.V" <aneesh.kumar at linux.vnet.ibm.com> writes:
> 
> > To support memory keys, we moved the hash pte slot information to the second
> > half of the page table. This was ok with PTE entries at level 4 and level 3.
> > We already allocate larger page table pages at those level to accomodate extra
> > details. For level 4 we already have the extra space which was used to track
> > 4k hash page table entry details and at pmd level the extra space was allocated
> > to track the THP details.
> >
> > With hugetlbfs PTE, we used this extra space at the PMD level to store the
> > slot details. But we also support hugetlbfs PTE at PUD leve and PUD level page
> > didn't allocate extra space. This resulted in memory corruption.
> >
> > Fix this by allocating extra space at PUD level when HUGETLB is enabled. We
> > may need further changes to allocate larger space at PMD level when we enable
> > HUGETLB. That will be done in next patch.
> >
> > Fixes:bf9a95f9a6481bc6e(" powerpc: Free up four 64K PTE bits in 64K backed HPTE pages")
> >
> > Signed-off-by: Aneesh Kumar K.V <aneesh.kumar at linux.vnet.ibm.com>
> 
> Another fix, I still get random memory corruption with hugetlb test with
> 16G hugepage config.

this fix may not be needed. It random corruption may be artifact of the typo you
had in your first patch?

RP