[PATCH] drm/amdgpu: Clear VRAM for DRM dumb_create buffers

[Kazlauskas, Nicholas]

On 3/11/19 12:58 PM, Christian König wrote:
> Am 08.03.19 um 17:47 schrieb Alex Deucher:
>> On Fri, Mar 8, 2019 at 10:38 AM Nicholas Kazlauskas
>> <nicholas.kazlauskas at amd.com> wrote:
>>> The dumb_create API isn't intended for high performance rendering
>>> and it's more useful for userspace (ie. IGT) to have them precleared.
>>>
>>> The bonus here is that we also won't needlessly leak whatever was
>>> previously in VRAM, but it also probably wasn't sensitive if it was
>>> going through this API.
>>>
>>> Signed-off-by: Nicholas Kazlauskas <nicholas.kazlauskas at amd.com>
>> Reviewed-by: Alex Deucher <alexander.deucher at amd.com>
> 
> NAK, IIRC we used to have this bit here before.
> 
> In general I agree that this would be a good idea, but the problem is 
> the that first dump buffer is sometimes created before the engine 
> (usually SDMA) to clear VRAM is initialized.
> 
> So you can run into a nice crash on suspend/resume.
> 
> Christian.

FWIW I never hit it myself during any suspend/resume tests I did but 
I'll take your word for it.

How about doing a map/memset/unmap immediately after buffer creation 
here? It'd be much slower, but it's also what we'd be doing in userspace 
anyway.

Nicholas Kazlauskas


> 
>>
>>> ---
>>>   drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c | 3 ++-
>>>   1 file changed, 2 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c 
>>> b/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c
>>> index fcaaac30e84b..a58072bbc9b8 100644
>>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c
>>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c
>>> @@ -743,7 +743,8 @@ int amdgpu_mode_dumb_create(struct drm_file 
>>> *file_priv,
>>>          domain = amdgpu_bo_get_preferred_pin_domain(adev,
>>>                                  
>>> amdgpu_display_supported_domains(adev));
>>>          r = amdgpu_gem_object_create(adev, args->size, 0, domain,
>>> -                                    
>>> AMDGPU_GEM_CREATE_CPU_ACCESS_REQUIRED,
>>> +                                    
>>> AMDGPU_GEM_CREATE_CPU_ACCESS_REQUIRED |
>>> +                                    AMDGPU_GEM_CREATE_VRAM_CLEARED,
>>>                                       ttm_bo_type_device, NULL, &gobj);
>>>          if (r)
>>>                  return -ENOMEM;
>>> -- 
>>> 2.17.1
>>>
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