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

[Aneesh Kumar K.V]

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:
>> 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.
> 
>>
>> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar at linux.vnet.ibm.com>
>> ---
>> NOTE: In the long run we may want to look at my patch series to remove slot
> ...snip...
>>   }
>>
>>   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