[PATCH] drm/ttm: fix pipelined gutting for evictions

[philip yang]

On 2020-07-23 7:02 p.m., Felix Kuehling wrote:
> Am 2020-07-23 um 5:00 a.m. schrieb Christian König:
>> We can't pipeline that during eviction because the memory needs
>> to be available immediately.
>>
>> Signed-off-by: Christian König <christian.koenig at amd.com>
>> ---
>>   drivers/gpu/drm/ttm/ttm_bo.c | 12 ++++++++++--
>>   1 file changed, 10 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/ttm/ttm_bo.c b/drivers/gpu/drm/ttm/ttm_bo.c
>> index bc2230ecb7e3..122040056a07 100644
>> --- a/drivers/gpu/drm/ttm/ttm_bo.c
>> +++ b/drivers/gpu/drm/ttm/ttm_bo.c
>> @@ -651,8 +651,16 @@ static int ttm_bo_evict(struct ttm_buffer_object *bo,
>>   	placement.num_busy_placement = 0;
>>   	bdev->driver->evict_flags(bo, &placement);
>>   
>> -	if (!placement.num_placement && !placement.num_busy_placement)
>> -		return ttm_bo_pipeline_gutting(bo);
>> +	if (!placement.num_placement && !placement.num_busy_placement) {
>> +		ttm_bo_wait(bo, false, false);
>> +
>> +		ttm_tt_destroy(bo->ttm);
>> +
>> +		memset(&bo->mem, 0, sizeof(bo->mem));
> Where does the memory in the bo->mem (ttm_mem_reg) get destroyed? It
> doesn't get attached to a ghost BO in this case, so someone will have to
> call ttm_bo_mem_put explicitly before you wipe out bo->mem.

After migrating to ram, 
svm_range_bo_unref-->amdgpu_unref_bo->ttm_bo_put->ttm_bo_release calls 
ttm_bo_mem_put.

vram is already freed before we signal fence, right?

Regards,

Philip

> Regards,
>    Felix
>
>
>> +		bo->mem.mem_type = TTM_PL_SYSTEM;
>> +		bo->ttm = NULL;
>> +		return 0;
>> +	}
>>   
>>   	evict_mem = bo->mem;
>>   	evict_mem.mm_node = NULL;