Re: [PATCH] drm/amdgpu: always allocate cleared VRAM for GEM allocations

["Christian König" <ckoenig.leichtzumerken@gmail.com>]

Am 29.07.24 um 12:42 schrieb Michel Dänzer:
> On 2024-07-26 17:25, Alex Deucher wrote:
>> On Fri, Jul 26, 2024 at 9:50 AM Alex Deucher <alexander.deucher@amd.com> wrote:
>>> This adds allocation latency, but aligns better with user
>>> expectations.  The latency should improve with the drm buddy
>>> clearing patches that Arun has been working on.
>>>
>>> Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
>>> ---
>>>   drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c | 4 ++++
>>>   1 file changed, 4 insertions(+)
>>>
>>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c
>>> index ebb3f87ef4f6..768840e8937d 100644
>>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c
>>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c
>>> @@ -347,6 +347,10 @@ int amdgpu_gem_create_ioctl(struct drm_device *dev, void *data,
>>>                  return -EINVAL;
>>>          }
>>>
>>> +       /* always clear VRAM */
>>> +       if (args->in.domains & AMDGPU_GEM_DOMAIN_VRAM)
>>> +               flags |= AMDGPU_GEM_CREATE_VRAM_CLEARED;
>> Alternatively, we can set AMDGPU_GEM_CREATE_VRAM_WIPE_ON_RELEASE here,
>> although for cases like reboots, we probably want clear on create.
> I agree. Thanks for doing this!

I strongly disagree. We have use cases were this will immediately become 
a problem.

Especially we won't be able to hold latency requirements on boot for 
certain projects any more.

Regards,
Christian.

>
> Reviewed-by: Michel Dänzer <mdaenzer@redhat.com>
>
>
> BTW, maybe this allows reducing the use of AMDGPU_GEM_CREATE_VRAM_WIPE_ON_RELEASE, or even eliminating it altogether? Does this leave any way for user space to access uncleared VRAM?
>
>