drm/amdgpu: Fix VM clean check method

amdgpu_vm_make_compute is used to turn a GFX VM into a compute VM,
the prerequisite is this VM is clean. Let's check if some page tables
are already filled , while not check if some mapping is already made.
Signed-off-by: Trigger Huang <Trigger.Huang@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c

@@ -2756,6 +2756,37 @@ int amdgpu_vm_init(struct amdgpu_device *adev, struct amdgpu_vm *vm,
 	return r;
 }
 
+/**
+ * amdgpu_vm_check_clean_reserved - check if a VM is clean
+ *
+ * @adev: amdgpu_device pointer
+ * @vm: the VM to check
+ *
+ * check all entries of the root PD, if any subsequent PDs are allocated,
+ * it means there are page table creating and filling, and is no a clean
+ * VM
+ *
+ * Returns:
+ *	0 if this VM is clean
+ */
+static int amdgpu_vm_check_clean_reserved(struct amdgpu_device *adev,
+	struct amdgpu_vm *vm)
+{
+	enum amdgpu_vm_level root = adev->vm_manager.root_level;
+	unsigned int entries = amdgpu_vm_num_entries(adev, root);
+	unsigned int i = 0;
+
+	if (!(vm->root.entries))
+		return 0;
+
+	for (i = 0; i < entries; i++) {
+		if (vm->root.entries[i].base.bo)
+			return -EINVAL;
+	}
+
+	return 0;
+}
+
 /**
  * amdgpu_vm_make_compute - Turn a GFX VM into a compute VM
  *
@@ -2786,10 +2817,9 @@ int amdgpu_vm_make_compute(struct amdgpu_device *adev, struct amdgpu_vm *vm, uns
 		return r;
 
 	/* Sanity checks */
-	if (!RB_EMPTY_ROOT(&vm->va.rb_root) || vm->root.entries) {
-		r = -EINVAL;
+	r = amdgpu_vm_check_clean_reserved(adev, vm);
+	if (r)
 		goto unreserve_bo;
-	}
 
 	if (pasid) {
 		unsigned long flags;