[PATCH V3 08/10] powerpc/mm/hash: Increase VA range to 128TB

[Aneesh Kumar K.V]

"Aneesh Kumar K.V" <aneesh.kumar at linux.vnet.ibm.com> writes:

> Michal Suchánek <msuchanek at suse.de> writes:
>
>> Hello,
>>
>> On Sun, 19 Feb 2017 15:37:15 +0530
>> "Aneesh Kumar K.V" <aneesh.kumar at linux.vnet.ibm.com> wrote:
>>
>>> We update the hash linux page table layout such that we can support
>>> 512TB. But we limit the TASK_SIZE to 128TB. We can switch to 128TB by
>>> default without conditional because that is the max virtual address
>>> supported by other architectures. We will later add a mechanism to
>>> on-demand increase the application's effective address range to 512TB.
>>> 
>>> Having the page table layout changed to accommodate 512TB  makes
>>> testing large memory configuration easier with less code changes to
>>> kernel
>>> 
>>> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar at linux.vnet.ibm.com>
>
> ....
>
>> index b64daf124fee..c7ca70dc3ba5 100644
>>> --- a/arch/powerpc/kernel/paca.c
>>> +++ b/arch/powerpc/kernel/paca.c
>>> @@ -253,8 +253,15 @@ void copy_mm_to_paca(struct mm_struct *mm)
>>>  	get_paca()->mm_ctx_id = context->id;
>>>  #ifdef CONFIG_PPC_MM_SLICES
>>>  	get_paca()->mm_ctx_low_slices_psize =
>>> context->low_slices_psize;
>>> +	/*
>>> +	 * We support upto 128TB for now. Hence copy only 128/2
>>> bytes.
>>> +	 * Later when we support tasks with different max effective
>>> +	 * address, we can optimize this based on mm->task_size.
>>> +	 */
>>> +	BUILD_BUG_ON(TASK_SIZE_USER64 != TASK_SIZE_128TB);
>>
>> Can this be handled by KConfig?
>> Above I see 
>
> I am reworking the series so that we depend on mm->task_size. Will send
> a new version soon.
>
>
>
>>> +#ifdef CONFIG_PPC_BOOK3S_64
>>> +#define TASK_SIZE_USER64 TASK_SIZE_128TB
>>> +#else
>>> +#define TASK_SIZE_USER64 TASK_SIZE_64TB
>>> +#endif
>> and 
>>> #ifdef CONFIG_PPC_MM_SLICES
>>> ILD_BUG_ON(TASK_SIZE_USER64 != TASK_SIZE_128TB)
>>
>> which boils down to
>> #ifndef CONFIG_PPC_BOOK3S_64
>> #ifdef CONFIG_PPC_MM_SLICES
>> #error TASK_SIZE_USER64 != TASK_SIZE_128TB
>>
>>
>>>  	memcpy(&get_paca()->mm_ctx_high_slices_psize,
>>> -	       &context->high_slices_psize, SLICE_ARRAY_SIZE);
>>> +	       &context->high_slices_psize, TASK_SIZE_128TB >> 41);
>>
>> Can we avoid magic numbers, please?
>>
>
> Since array is 4 bytes per each TB which is documented else where.

4 bits per teach TB.


-aneesh