Re: [PATCH 3/3] drm/amdgpu: skip kfd resume_process for dev_pm_ops.thaw()

["Christian König" <christian.koenig@amd.com>]

On 01.07.25 10:03, Zhang, GuoQing (Sam) wrote:
> 
> thaw() is called before writing the hiberation image to swap disk. See
> the doc here.
> https://github.com/torvalds/linux/blob/v6.14/Documentation/driver-api/pm/devices.rst?plain=1#L552 <https://github.com/torvalds/linux/blob/v6.14/Documentation/driver-api/pm/devices.rst?plain=1#L552>
> 
> And amdgpu implemented thaw() callback by calling amdgpu_device_resume().
> https://github.com/torvalds/linux/blob/v6.14/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c#L2572 <https://github.com/torvalds/linux/blob/v6.14/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c#L2572>
> 
> This patch is skip amdgpu_amdkfd_resume_process() call in thaw() during
> hibernation. it is not skipped in restore() during resume from
> hibernation when system boot again.
> 
> 
> I just found the following kernel doc. Thaw() is intended to resume the
> storage device for saving the hibernation image.

Ah, that makes much more sense.

> Our GPU is not involved
> in it, it is not necessary to resume our GPU in thaw().
> https://github.com/torvalds/linux/blob/v6.14/Documentation/power/pci.rst?plain=1#L588 <https://github.com/torvalds/linux/blob/v6.14/Documentation/power/pci.rst?plain=1#L588>
> 
> So another implementation is to remove the amdgpu_device_resume() call
> in amdgpu_pmops_thaw(), and skip amdgpu_device_ip_suspend() call in
> amdgpu_pci_shutdown()for hibernation.
> Initial tests show it's working fine for hibernation successful case.
> Should I switch to this implementation?

No idea. Alex and the KFD guys need to take a look at that.

> But thaw() is also called to restore the GPU when hibernation is aborted
> due to some error in hibernation image creation stage. In this case,
> amdgpu_device_resume() is needed in thaw().
> 
> So I need a method to check if hibernation is aborted or not to
> conditionally skip amdgpu_device_resume() in thaw(). Currently I don't
> know how to do this.

Yeah that approach here looks fishy to me, but I don't know how to properly fix it either.

@Alex any idea?

Regards,
Christian.

> 
> 
> Regards
> Sam
> 
> 
> On 2025/6/30 19:58, Christian König wrote:
>> On 30.06.25 12:41, Samuel Zhang wrote:
>>> The hibernation successful workflow:
>>> - prepare: evict VRAM and swapout GTT BOs
>>> - freeze
>>> - create the hibernation image in system memory
>>> - thaw: swapin and restore BOs
>> Why should a thaw happen here in between?
>>
>>> - complete
>>> - write hibernation image to disk
>>> - amdgpu_pci_shutdown
>>> - goto S5, turn off the system.
>>>
>>> During prepare stage of hibernation, VRAM and GTT BOs will be swapout to
>>> shmem. Then in thaw stage, all BOs will be swapin and restored.
>> That's not correct. This is done by the application starting again and not during thaw.
>>
>>> On server with 192GB VRAM * 8 dGPUs and 1.7TB system memory,
>>> the swapin and restore BOs takes too long (50 minutes) and it is not
>>> necessary since the follow-up stages does not use GPU.
>>>
>>> This patch is to skip BOs restore during thaw to reduce the hibernation
>>> time.
>> As far as I can see that doesn't make sense. The KFD processes need to be resumed here and that can't be skipped.
>>
>> Regards,
>> Christian.
>>
>>> Signed-off-by: Samuel Zhang <guoqing.zhang@amd.com>
>>> ---
>>>   drivers/gpu/drm/amd/amdgpu/amdgpu_device.c | 2 +-
>>>   drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c    | 2 ++
>>>   2 files changed, 3 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
>>> index a8f4697deb1b..b550d07190a2 100644
>>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
>>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
>>> @@ -5328,7 +5328,7 @@ int amdgpu_device_resume(struct drm_device *dev, bool notify_clients)
>>>               amdgpu_virt_init_data_exchange(adev);
>>>               amdgpu_virt_release_full_gpu(adev, true);
>>>   
>>> -            if (!adev->in_s0ix && !r && !adev->in_runpm)
>>> +            if (!adev->in_s0ix && !r && !adev->in_runpm && !adev->in_s4)
>>>                       r = amdgpu_amdkfd_resume_process(adev);
>>>       }
>>>   
>>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
>>> index 571b70da4562..23b76e8ac2fd 100644
>>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
>>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
>>> @@ -2734,7 +2734,9 @@ static int amdgpu_pmops_poweroff(struct device *dev)
>>>   static int amdgpu_pmops_restore(struct device *dev)
>>>   {
>>>       struct drm_device *drm_dev = dev_get_drvdata(dev);
>>> +    struct amdgpu_device *adev = drm_to_adev(drm_dev);
>>>   
>>> +    adev->in_s4 = false;
>>>       return amdgpu_device_resume(drm_dev, true);
>>>   }
>>>   
>