Re: [PATCH 1/3] drm/nouveau: wait for moving fence after pinning

["Christian König" <ckoenig.leichtzumerken@gmail.com>]

Am 21.06.21 um 16:54 schrieb Daniel Vetter:
> On Mon, Jun 21, 2021 at 03:03:26PM +0200, Christian König wrote:
>> We actually need to wait for the moving fence after pinning
>> the BO to make sure that the pin is completed.
>>
>> Signed-off-by: Christian König <christian.koenig@amd.com>
>> CC: stable@kernel.org
>> ---
>>   drivers/gpu/drm/nouveau/nouveau_prime.c | 8 +++++++-
>>   1 file changed, 7 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/gpu/drm/nouveau/nouveau_prime.c b/drivers/gpu/drm/nouveau/nouveau_prime.c
>> index 347488685f74..591738545eba 100644
>> --- a/drivers/gpu/drm/nouveau/nouveau_prime.c
>> +++ b/drivers/gpu/drm/nouveau/nouveau_prime.c
>> @@ -93,7 +93,13 @@ int nouveau_gem_prime_pin(struct drm_gem_object *obj)
>>   	if (ret)
>>   		return -EINVAL;
>>   
>> -	return 0;
>> +	if (nvbo->bo.moving) {
> Don't we need to hold the dma_resv to read this? We can grab a reference
> and then unlock, but I think just unlocked wait can go boom pretty easily
> (since we don't hold a reference or lock so someone else can jump in and
> free the moving fence).

The moving fence is only modified while the BO is moved and since we 
have just successfully pinned it....

But in general I agree that it would be better to avoid this. I just 
didn't wanted to open a bigger can of worms by changing nouveau so much.

Christian.

> -Daniel
>
>> +		ret = dma_fence_wait(nvbo->bo.moving, true);
>> +		if (ret)
>> +			nouveau_bo_unpin(nvbo);
>> +	}
>> +
>> +	return ret;
>>   }
>>   
>>   void nouveau_gem_prime_unpin(struct drm_gem_object *obj)
>> -- 
>> 2.25.1
>>

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