[PATCH] drm/ttm: update bulk move object of ghost BO

[Yin, ZhenGuo (Chris)]

Inside the function ttm_bo_set_bulk_move, it calls 
ttm_resource_del_bulk_move to remove the old resource from the bulk_move 
list.

If we set the bulk_move to NULL manually as suggested, the old resource 
attached in the ghost BO seems won't be removed from the bulk_move.

On 9/1/2022 7:13 PM, Christian König wrote:
> Am 01.09.22 um 13:11 schrieb Christian König:
>> Am 01.09.22 um 11:29 schrieb ZhenGuo Yin:
>>> [Why]
>>> Ghost BO is released with non-empty bulk move object. There is a
>>> warning trace:
>>> WARNING: CPU: 19 PID: 1582 at ttm/ttm_bo.c:366 
>>> ttm_bo_release+0x2e1/0x2f0 [amdttm]
>>> Call Trace:
>>>    amddma_resv_reserve_fences+0x10d/0x1f0 [amdkcl]
>>>    amdttm_bo_put+0x28/0x30 [amdttm]
>>>    amdttm_bo_move_accel_cleanup+0x126/0x200 [amdttm]
>>>    amdgpu_bo_move+0x1a8/0x770 [amdgpu]
>>>    ttm_bo_handle_move_mem+0xb0/0x140 [amdttm]
>>>    amdttm_bo_validate+0xbf/0x100 [amdttm]
>>>
>>> [How]
>>> The resource of ghost BO should be moved to LRU directly, instead of
>>> using bulk move. The bulk move object of ghost BO should set to NULL
>>> before function ttm_bo_move_to_lru_tail_unlocked.
>>>
>>> Fixed:·5b951e487fd6bf5f·("drm/ttm:·fix·bulk·move·handling·v2")
>>> Signed-off-by: ZhenGuo Yin <zhenguo.yin at amd.com>
>>
>> Good catch, but the fix is not 100% correct. Please rather just NULL 
>> the member while initializing the BO structure.
>>
>> E.g. something like this:
>>
>>  ....
>>  fbo->base.pin_count = 0;
>> +fbo->base.bulk_move= NULL;
>>  if (bo->type != ttm_bo_type_sg)
>>  ....
>
> On the other hand thinking about it that won't work either.
>
> You need to set bulk_move to NULL manually in an else clauses or 
> something like this.
>
> Regards,
> Christian.
>
>>
>> Thanks,
>> Christian.
>>
>>> ---
>>>   drivers/gpu/drm/ttm/ttm_bo_util.c | 1 +
>>>   1 file changed, 1 insertion(+)
>>>
>>> diff --git a/drivers/gpu/drm/ttm/ttm_bo_util.c 
>>> b/drivers/gpu/drm/ttm/ttm_bo_util.c
>>> index 1cbfb00c1d65..a90bbbd91910 100644
>>> --- a/drivers/gpu/drm/ttm/ttm_bo_util.c
>>> +++ b/drivers/gpu/drm/ttm/ttm_bo_util.c
>>> @@ -238,6 +238,7 @@ static int ttm_buffer_object_transfer(struct 
>>> ttm_buffer_object *bo,
>>>         if (fbo->base.resource) {
>>>           ttm_resource_set_bo(fbo->base.resource, &fbo->base);
>>> +        ttm_bo_set_bulk_move(&fbo->base, NULL);
>>>           bo->resource = NULL;
>>>       }
>>
>