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

[Aneesh Kumar K.V]

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.
Considering we are just converting max range there, do we need that as a
macro ?

-aneesh