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

[Sam <guoqzhan@amd.com>]

On 2025/7/2 00:07, Alex Deucher wrote:
> On Tue, Jul 1, 2025 at 4:32 AM Christian König <christian.koenig@amd.com> wrote:
>> 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?
> Yeah, I'm not sure how to handle that.  I don't see a way to avoid
> having all of the callbacks.  We could ideally skip some of the steps.
> Maybe we could optimize the freeze and thaw routines if we had some
> hint from the pm core about why we were getting called.  E.g., thaw
> after a failed hibernation restore.
>
> Alex


I just found pm_transition variable can be used to check if hibernation 
is cancelled (PM_EVENT_RECOVER) or not(PM_EVENT_THAW) in thaw(). I just 
need to export this variable in kernel.
https://github.com/torvalds/linux/blob/master/drivers/base/power/main.c#L64

Provided pm_transition is available, should we skip 
amdgpu_amdkfd_resume_process() only, or skip amdgpu_device_resume() 
completely?

Regards
Sam


>
>> 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);
>>>>>    }
>>>>>