[PATCH 3/4] drm/amdgpu: reserve root PD while releasing it

[Lyude Paul]

From: Christian König <christian.koe...@amd.com>

Otherwise somebody could try to evict it at the same time and try to use
half torn down structures.

commit 2642cf110d08a403f585a051e4cbf45a90b3adea upstream

Signed-off-by: Christian König <christian.koe...@amd.com>
Reviewed-and-Tested-by: Michel Dänzer <michel.daen...@amd.com>
Reviewed-by: Alex Deucher <alexander.deuc...@amd.com>
Signed-off-by: Alex Deucher <alexander.deuc...@amd.com>
Signed-off-by: Lyude Paul <ly...@redhat.com>
---
 drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c 
b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
index bd20ff018512..591c6dc2c1f7 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
@@ -2586,7 +2586,8 @@ void amdgpu_vm_fini(struct amdgpu_device *adev, struct 
amdgpu_vm *vm)
 {
        struct amdgpu_bo_va_mapping *mapping, *tmp;
        bool prt_fini_needed = !!adev->gart.gart_funcs->set_prt;
-       int i;
+       struct amdgpu_bo *root;
+       int i, r;
 
        amd_sched_entity_fini(vm->entity.sched, &vm->entity);
 
@@ -2609,7 +2610,15 @@ void amdgpu_vm_fini(struct amdgpu_device *adev, struct 
amdgpu_vm *vm)
                amdgpu_vm_free_mapping(adev, vm, mapping, NULL);
        }
 
-       amdgpu_vm_free_levels(&vm->root);
+       root = amdgpu_bo_ref(vm->root.bo);
+       r = amdgpu_bo_reserve(root, true);
+       if (r) {
+               dev_err(adev->dev, "Leaking page tables because BO reservation 
failed\n");
+       } else {
+               amdgpu_vm_free_levels(&vm->root);
+               amdgpu_bo_unreserve(root);
+       }
+       amdgpu_bo_unref(&root);
        dma_fence_put(vm->last_dir_update);
        for (i = 0; i < AMDGPU_MAX_VMHUBS; i++)
                amdgpu_vm_free_reserved_vmid(adev, vm, i);
-- 
2.14.3