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

[Christian König]

Am 25.06.2018 um 11:07 schrieb Michel Dänzer:
> From: Michel Dänzer <michel.daenzer at 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.

Regards,
Christian.

>
> Cc: stable at vger.kernel.org
> Bugzilla: https://bugs.freedesktop.org/106418
> Reported-by: mikhail.v.gavrilov at gmail.com
> Signed-off-by: Michel Dänzer <michel.daenzer at 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);
>