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

On 02/09/2018 12:52 AM, Ram Pai wrote:

On Thu, Feb 08, 2018 at 04:04:41PM +0530, Aneesh Kumar K.V wrote:

quoted

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")

hmm.. did not know that hugetlbs operated at the PUD level. Thanks for
catching this.

quoted

Signed-off-by: Aneesh Kumar K.V <redacted>
---
NOTE: In the long run we may want to look at my patch series to remove slot

...snip...

quoted

  }

  static inline pmd_t *pmd_alloc_one(struct mm_struct *mm, unsigned long addr)

diff --git a/arch/powerpc/include/asm/book3s/64/pgtable.h b/arch/powerpc/include/asm/book3s/64/pgtable.h
index 51017726d495..3c14663d457d 100644
--- a/arch/powerpc/include/asm/book3s/64/pgtable.h
+++ b/arch/powerpc/include/asm/book3s/64/pgtable.h

@@ -232,11 +232,13 @@ extern unsigned long __pmd_index_size;
  extern unsigned long __pud_index_size;
  extern unsigned long __pgd_index_size;
  extern unsigned long __pmd_cache_index;
+extern unsigned long __pud_cache_index;
  #define PTE_INDEX_SIZE  __pte_index_size
  #define PMD_INDEX_SIZE  __pmd_index_size
  #define PUD_INDEX_SIZE  __pud_index_size
  #define PGD_INDEX_SIZE  __pgd_index_size
  #define PMD_CACHE_INDEX __pmd_cache_index
+#define PUD_CACHE_INDEX __pmd_cache_index

This is a typo. Should be 'pud' not a 'pmd'.

#define PUD_CACHE_INDEX __pud_cache_index

Thanks fixed that.

-aneesh