[PATCH 1/2] drm/amdgpu: don't clean the framebuffer for VF

[Christian König]

Hi Pixel,

you don't seem to understand the reason for the clear here.

It is completely irrelevant that the host is clearing the memory for the 
guest, the problem is that the guest reuse the memory it got assigned 
from the host multiple times.

IIRC we added this because you could see leftovers of the slash screen 
in the text console when the resolution wasn't a multiple of the 
character height.

Regards,
Christian.

Am 06.02.2017 um 10:09 schrieb Ding, Pixel:
> Hi Christian,
>
> The underlying host driver clears VF’s framebuffer when guest driver shake hands with it, that is done before guest driver init. I think it’s unnecessary to clear FB again even with GPU for VF.
>
> —
> Sincerely Yours,
> Pixel
>
>
>
>
>
> On 06/02/2017, 4:49 PM, "Koenig, Christian" <Christian.Koenig at amd.com> wrote:
>
>> Am 06.02.2017 um 07:24 schrieb Pixel Ding:
>>> The SRIOV host driver cleans framebuffer for each VF, guest driver
>>> needn't this action which costs much time on some virtualization
>>> platform, otherwise it might get timeout to initialize.
>>>
>>> Signed-off-by: Pixel Ding <Pixel.Ding at amd.com>
>>> ---
>>>    drivers/gpu/drm/amd/amdgpu/amdgpu_fb.c | 4 +++-
>>>    1 file changed, 3 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_fb.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_fb.c
>>> index 1e735c4..f1eb4f5 100644
>>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_fb.c
>>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_fb.c
>>> @@ -242,7 +242,9 @@ static int amdgpufb_create(struct drm_fb_helper *helper,
>>>    	/* setup helper */
>>>    	rfbdev->helper.fb = fb;
>>>    
>>> -	memset_io(abo->kptr, 0x0, amdgpu_bo_size(abo));
>>> +	if (!amdgpu_sriov_vf(adev)) {
>>> +		memset_io(abo->kptr, 0x0, amdgpu_bo_size(abo));
>>> +	}
>> Nit pick only, but coding style says to not use "{" "}" in an if without
>> else and only a single line of code.
>>
>> Additional to that I'm not sure if that's a good idea. The memory
>> allocated here might be already be used and so we need to clear it no
>> matter where it came from.
>>
>> It's probably easier to just set the AMDGPU_GEM_CREATE_VRAM_CLEARED in
>> the call to amdgpu_gem_object_create(). This makes the GPU clear the
>> memory before the first CPU access to it.
>>
>> Regards,
>> Christian.
>>
>>>    
>>>    	strcpy(info->fix.id, "amdgpudrmfb");
>>>    
>>