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

["Zhang, GuoQing (Sam)" <guoqzhan@amd.com>]

On 2025/7/2 22:07, Lazar, Lijo wrote:
>
> On 7/2/2025 7:24 PM, Alex Deucher wrote:
>> On Wed, Jul 2, 2025 at 3:24 AM Sam <guoqzhan@amd.com> wrote:
>>>
>>> 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?
>> Hmmm.  Still not sure how best to handle this.  For entering
>> hibernation, all we really need is freeze().  Once we are done with
>> that we don't need thaw() or poweroff() for hibernation as we've
>> already suspended in freeze() so there is nothing else to do.  For
>> exiting hibernation, we need freeze() to suspend and then either
>> thaw() (if the hibernation image is bad) or restore() (if the
>> hibernation image is good) to resume.
>>
> If pm_transition is available, we can keep thaw() as we have now and do
> resume only if pm_transition =  PM_EVENT_RECOVER. shutdown() may check
> in_s4 and do nothing.


Hi Lijo, Christian and Alex,
Thank you for the suggestion and feedback. I have implemented this 
behavior and send out the v2 patch list. Please help review. Thank you!

[PATCH v2 0/5] reduce system memory requirement for hibernation
[PATCH v2 1/5] drm/ttm: add ttm_device_prepare_hibernation() api
[PATCH v2 2/5] drm/amdgpu: move GTT to shmem after eviction for hibernation
[PATCH v2 3/5] PM: hibernate: shrink shmem pages after dev_pm_ops.prepare()
[PATCH v2 4/5] PM: hibernate: export variable pm_transition
[PATCH v2 5/5] drm/amdgpu: do not resume device in thaw for normal 
hibernation

Regards
Sam


>
> Thanks,
> Lijo
>
>
>> Alex
>>
>>> 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);
>>>>>>>>     }
>>>>>>>>