[PATCH v3 05/12] drm/ttm: Expose ttm_tt_unpopulate for driver use

[Christian König]

Am 23.11.20 um 21:38 schrieb Andrey Grodzovsky:
>
> On 11/23/20 3:20 PM, Christian König wrote:
>> Am 23.11.20 um 21:05 schrieb Andrey Grodzovsky:
>>>
>>> On 11/25/20 5:42 AM, Christian König wrote:
>>>> Am 21.11.20 um 06:21 schrieb Andrey Grodzovsky:
>>>>> It's needed to drop iommu backed pages on device unplug
>>>>> before device's IOMMU group is released.
>>>>
>>>> It would be cleaner if we could do the whole handling in TTM. I 
>>>> also need to double check what you are doing with this function.
>>>>
>>>> Christian.
>>>
>>>
>>> Check patch "drm/amdgpu: Register IOMMU topology notifier per 
>>> device." to see
>>> how i use it. I don't see why this should go into TTM mid-layer - 
>>> the stuff I do inside
>>> is vendor specific and also I don't think TTM is explicitly aware of 
>>> IOMMU ?
>>> Do you mean you prefer the IOMMU notifier to be registered from 
>>> within TTM
>>> and then use a hook to call into vendor specific handler ?
>>
>> No, that is really vendor specific.
>>
>> What I meant is to have a function like 
>> ttm_resource_manager_evict_all() which you only need to call and all 
>> tt objects are unpopulated.
>
>
> So instead of this BO list i create and later iterate in amdgpu from 
> the IOMMU patch you just want to do it within
> TTM with a single function ? Makes much more sense.

Yes, exactly.

The list_empty() checks we have in TTM for the LRU are actually not the 
best idea, we should now check the pin_count instead. This way we could 
also have a list of the pinned BOs in TTM.

BTW: Have you thought about what happens when we unpopulate a BO while 
we still try to use a kernel mapping for it? That could have unforeseen 
consequences.

Christian.

>
> Andrey
>
>
>>
>> Give me a day or two to look into this.
>>
>> Christian.
>>
>>>
>>> Andrey
>>>
>>>
>>>>
>>>>>
>>>>> Signed-off-by: Andrey Grodzovsky <andrey.grodzovsky at amd.com>
>>>>> ---
>>>>>   drivers/gpu/drm/ttm/ttm_tt.c | 1 +
>>>>>   1 file changed, 1 insertion(+)
>>>>>
>>>>> diff --git a/drivers/gpu/drm/ttm/ttm_tt.c 
>>>>> b/drivers/gpu/drm/ttm/ttm_tt.c
>>>>> index 1ccf1ef..29248a5 100644
>>>>> --- a/drivers/gpu/drm/ttm/ttm_tt.c
>>>>> +++ b/drivers/gpu/drm/ttm/ttm_tt.c
>>>>> @@ -495,3 +495,4 @@ void ttm_tt_unpopulate(struct ttm_tt *ttm)
>>>>>       else
>>>>>           ttm_pool_unpopulate(ttm);
>>>>>   }
>>>>> +EXPORT_SYMBOL(ttm_tt_unpopulate);
>>>>
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>>