Deprecation of AMDGPU_GEM_CREATE_CPU_ACCESS_REQUIRED

[Christian König]

Am 30.06.2017 um 03:36 schrieb Michel Dänzer:
> On 30/06/17 12:03 AM, Marek Olšák wrote:
>> Do you have any concern if we also stop using the CPU_ACCESS flag on radeon?
> No concern from my side for radeon.
>
>
>> On Thu, Jun 29, 2017 at 4:51 PM, Christian König
>> <deathsimple at vodafone.de> wrote:
>>> Yeah, I was thinking something similar.
>>>
>>> See the intention behind CPU_ACCESS_REQUIRED is to always guarantee that CPU
>>> access is immediately possible.
>>>
>>> If you ask me that is not really useful for the UMD and was never meant to
>>> be used by Mesa (only the closed source UMD and some kernel internal use
>>> cases).
>>>
>>> I would like to keep the behavior in the kernel driver as it is, but we
>>> should really stop using this as a hint in Mesa.
> So we'd have a flag in the userspace ABI which is only used by closed
> source userspace, and which can be used to artificially create pressure
> on CPU visible VRAM. I know somebody who would argue vehemently against
> adding something like that. :)

Yeah, and I really tried hard to prevent that :)

But unfortunately the milk is already spilled, so not much we can do 
about that.

> What does the closed source UMD use the flag for?

Well it doesn't use the flag, but it has the concept of separate heaps 
for visible and invisible VRAM and maps that to setting the flag 
appropriately.

But putting the closed source UMD asside, my primary concern is rather 
in kernel users of the flag.

Regards,
Christian.