Re: [PATCH v2] drm/amdgpu: Reserve shared fence slot in amdgpu_vm_update_directories

["Zhang, Jerry (Junwei)" <Jerry.Zhang-5C7GfCeVMHo@public.gmane.org>]

On 07/02/2018 05:23 PM, Christian König wrote:
> Am 25.06.2018 um 11:07 schrieb Michel Dänzer:
>> From: Michel Dänzer <michel.daenzer@amd.com>
>>
>> Without this, there could not be enough slots, which could trigger the
>> BUG_ON in reservation_object_add_shared_fence.
>>
>> v2:
>> * Jump to the error label instead of returning directly (Jerry Zhang)
>
> Well good catch, but NAK that is not the right solution to the issue.
>
> amdgpu_vm_update_directories() is only called by two places, the first one is amdgpu_bo_vm_update_pte() and the second amdgpu_gem_va_update_vm().
>
> In both cases the directory is reserved using ttm_eu_reserve_buffers() with "entry->tv.shared = true;".
>
> What most likely needs to be done instead is to call reservation_object_reserve_shared() after all the VM operations in amdgpu_bo_vm_update_pte() to make sure that we still have one additional slot
> for the command submission.

In this case, it looks like amdgpu_vm_bo_update_mapping() handling, inside ttm_eu_reserve_buffers() as well.

Is there any specific reason to call it at the end of amdgpu_bo_vm_update_pte()?

AFAIW, that has to be called right before where to add shared slot.

Jerry

>
> Regards,
> Christian.
>
>>
>> Cc: stable@vger.kernel.org
>> Bugzilla: https://bugs.freedesktop.org/106418
>> Reported-by: mikhail.v.gavrilov@gmail.com
>> Signed-off-by: Michel Dänzer <michel.daenzer@amd.com>
>> ---
>>   drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c | 4 ++++
>>   1 file changed, 4 insertions(+)
>>
>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
>> index 590db78b8c72..579bcc33d544 100644
>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
>> @@ -1111,6 +1111,10 @@ int amdgpu_vm_update_directories(struct amdgpu_device *adev,
>>           struct amdgpu_ring *ring;
>>           struct dma_fence *fence;
>> +        r = reservation_object_reserve_shared(root->tbo.resv);
>> +        if (r)
>> +            goto error;
>> +
>>           ring = container_of(vm->entity.sched, struct amdgpu_ring,
>>                       sched);
>
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