[PATCH] drm/amdgpu: add flag for high priority contexts

[Andres Rodriguez]

Hey Serguei


On 2017-01-04 07:56 AM, Christian König wrote:
> Am 04.01.2017 um 12:03 schrieb Sagalovitch, Serguei:
>> Andres,
>>
>> I have on rather generic design question:
>>
>> Why we want to restrict it to CAP_SYS_ADMIN?
>>
>> +       if (priority == AMD_SCHED_PRIORITY_HIGH && 
>> !capable(CAP_SYS_ADMIN))
>> +               return -EACCES;
>>
>> Should we make it generic? My understanding is that If we follow 
>> "nice" semantic
>> then it will not require such privilege.
>
> Well it follows the "nice" semantic, the the documentation of the nice 
> system call:
>
>        nice()  adds inc to the nice value for the calling process. (A 
> higher nice value means a low priority.)  Only the superuser may 
> specify a negative increment, or priority increase.  The range
>        for nice values is described in getpriority(2).
>
> Of course the nice limit is more fine grained these days. IIRC it was 
> a soft resource limit now the last time I looked.
>
> We would essentially need something similar for the GPU if we want to 
> allow a regular process to get a higher priority.

As Christian mentioned this is based on the same restrictions as nice.

Also thinking along the lines of, it would be easier in the future to 
relax requirements than to increase them.

If we end up in a scenario where we want looser restrictions, that can 
be implemented as a new feature.

However, the opposite is not true. If we require to tighten restrictions 
that would result in an backwards compatibility breakage, and the patch 
would not be allowed. Apps that used to have access no longer have access.

Regards,
Andres

>
> Regards,
> Christian.
>
>>
>> Sincerely yours,
>> Serguei Sagalovitch
>>
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