[PATCH v3 03/13] mm/debug_vm_pgtable/ppc64: Avoid setting top bits in radom value

[Anshuman Khandual]

On 09/01/2020 11:51 AM, Aneesh Kumar K.V wrote:
> On 9/1/20 8:45 AM, Anshuman Khandual wrote:
>>
>>
>> On 08/27/2020 01:34 PM, Aneesh Kumar K.V wrote:
>>> ppc64 use bit 62 to indicate a pte entry (_PAGE_PTE). Avoid setting that bit in
>>> random value.
>>>
>>> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar at linux.ibm.com>
>>> ---
>>>   mm/debug_vm_pgtable.c | 13 ++++++++++---
>>>   1 file changed, 10 insertions(+), 3 deletions(-)
>>>
>>> diff --git a/mm/debug_vm_pgtable.c b/mm/debug_vm_pgtable.c
>>> index 086309fb9b6f..bbf9df0e64c6 100644
>>> --- a/mm/debug_vm_pgtable.c
>>> +++ b/mm/debug_vm_pgtable.c
>>> @@ -44,10 +44,17 @@
>>>    * entry type. But these bits might affect the ability to clear entries with
>>>    * pxx_clear() because of how dynamic page table folding works on s390. So
>>>    * while loading up the entries do not change the lower 4 bits. It does not
>>> - * have affect any other platform.
>>> + * have affect any other platform. Also avoid the 62nd bit on ppc64 that is
>>> + * used to mark a pte entry.
>>>    */
>>> -#define S390_MASK_BITS    4
>>> -#define RANDOM_ORVALUE    GENMASK(BITS_PER_LONG - 1, S390_MASK_BITS)
>>> +#define S390_SKIP_MASK        GENMASK(3, 0)
>>> +#ifdef CONFIG_PPC_BOOK3S_64
>>> +#define PPC64_SKIP_MASK        GENMASK(62, 62)
>>> +#else
>>> +#define PPC64_SKIP_MASK        0x0
>>> +#endif
>>
>> Please drop the #ifdef CONFIG_PPC_BOOK3S_64 here. We already accommodate skip
>> bits for a s390 platform requirement and can also do so for ppc64 as well. As
>> mentioned before, please avoid adding any platform specific constructs in the
>> test.
>>
> 
> 
> that is needed so that it can be built on 32 bit architectures.I did face build errors with arch-linux

Could not (#if __BITS_PER_LONG == 32) be used instead or something like
that. But should be a generic conditional check identifying 32 bit arch
not anything platform specific.