Re: [PATCH] drm/amdgpu: avoid null dereference of fence when using cpu to update page tables

[Christian König]

Am 05.05.23 um 11:10 schrieb Lang Yu:
Using cpu to update page tables is sychronous, no need to wait fence
and it is NULL in such a case.

Good catch, be we usually install the stub into fence pointers when they 
are unused. See dma_fence_get_stub().

Christian.


Signed-off-by: Lang Yu <lang...@amd.com>
---
  drivers/gpu/drm/amd/amdgpu/amdgpu_mes.c | 7 +++++--
  1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_mes.c 
b/drivers/gpu/drm/amd/amdgpu/amdgpu_mes.c
index f0f00466b59f..197981c4ac7d 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_mes.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_mes.c
@@ -1043,8 +1043,11 @@ int amdgpu_mes_add_ring(struct amdgpu_device *adev, int 
gang_id,
  
  	amdgpu_mes_ring_to_queue_props(adev, ring, &qprops);
  
-	dma_fence_wait(gang->process->vm->last_update, false);
-       dma_fence_wait(ctx_data->meta_data_va->last_pt_update, false);
+       if (gang->process->vm->last_update)
+               dma_fence_wait(gang->process->vm->last_update, false);
+       if (ctx_data->meta_data_va->last_pt_update)
+               dma_fence_wait(ctx_data->meta_data_va->last_pt_update, false);
+
        amdgpu_mes_unlock(&adev->mes);
  
  	r = amdgpu_mes_add_hw_queue(adev, gang_id, &qprops, &queue_id);