drm/amdgpu: install stub fence into potential unused fence pointers

When using cpu to update page tables, vm update fences are unused.
Install stub fence into these fence pointers instead of NULL
to avoid NULL dereference when calling dma_fence_wait() on them.

Suggested-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Lang Yu <Lang.Yu@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
index 3c0310576b3bfb515d9dccc2cc3e6fffd935d80e..b6bd667df6763ffb444074840019431284f1dbae 100644 (file)
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
@@ -1358,6 +1358,7 @@ struct amdgpu_bo_va *amdgpu_vm_bo_add(struct amdgpu_device *adev,
        amdgpu_vm_bo_base_init(&bo_va->base, vm, bo);
 
        bo_va->ref_count = 1;
+       bo_va->last_pt_update = dma_fence_get_stub();
        INIT_LIST_HEAD(&bo_va->valids);
        INIT_LIST_HEAD(&bo_va->invalids);
 
@@ -2067,7 +2068,8 @@ int amdgpu_vm_init(struct amdgpu_device *adev, struct amdgpu_vm *vm)
                vm->update_funcs = &amdgpu_vm_cpu_funcs;
        else
                vm->update_funcs = &amdgpu_vm_sdma_funcs;
-       vm->last_update = NULL;
+
+       vm->last_update = dma_fence_get_stub();
        vm->last_unlocked = dma_fence_get_stub();
        vm->last_tlb_flush = dma_fence_get_stub();
 
@@ -2192,7 +2194,7 @@ int amdgpu_vm_make_compute(struct amdgpu_device *adev, struct amdgpu_vm *vm)
                goto unreserve_bo;
 
        dma_fence_put(vm->last_update);
-       vm->last_update = NULL;
+       vm->last_update = dma_fence_get_stub();
        vm->is_compute_context = true;
 
        /* Free the shadow bo for compute VM */