drm/amdgpu: fix VM page table reference counting

We use the reservation object of the page directory for the page tables as
well, because of this the page directory should be freed last. Ensure that
by keeping a reference from the page tables to the directory.

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

3 files changed, 7 insertions, 0 deletions

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu.h b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
index 251b14736de9..670fefb56945 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu.h
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
@@ -539,6 +539,7 @@ struct amdgpu_bo {
         /* Constant after initialization */
         struct amdgpu_device            *adev;
         struct drm_gem_object           gem_base;
+        struct amdgpu_bo                *parent;
 
         struct ttm_bo_kmap_obj          dma_buf_vmap;
         pid_t                           pid;
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_object.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_object.c
index 0d524384ff79..c3ce103b6a33 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_object.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_object.c
@@ -100,6 +100,7 @@ static void amdgpu_ttm_bo_destroy(struct ttm_buffer_object *tbo)
         list_del_init(&bo->list);
         mutex_unlock(&bo->adev->gem.mutex);
         drm_gem_object_release(&bo->gem_base);
+        amdgpu_bo_unref(&bo->parent);
         kfree(bo->metadata);
         kfree(bo);
 }
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
index ae037e5b6ad0..a582ef553499 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
@@ -1079,6 +1079,11 @@ int amdgpu_vm_bo_map(struct amdgpu_device *adev,
                 if (r)
                         goto error_free;
 
+                /* Keep a reference to the page table to avoid freeing
+                 * them up in the wrong order.
+                 */
+                pt->parent = amdgpu_bo_ref(vm->page_directory);
+
                 r = amdgpu_vm_clear_bo(adev, pt);
                 if (r) {
                         amdgpu_bo_unref(&pt);