drm/xe/vm: Defer vm rebind until next exec if nothing to execute

If all compute engines of a vm in compute mode are idle,
defer a rebind to the next exec to avoid the VM unnecessarily trying
to make memory resident and compete with other VMs for available
memory space.
Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Reviewed-by: Matthew Brost <matthew.brost@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>

drivers/gpu/drm/xe/xe_exec.c

@@ -364,6 +364,7 @@ int xe_exec_ioctl(struct drm_device *dev, void *data, struct drm_file *file)
 				     &job->drm.s_fence->finished);
 
 	xe_sched_job_push(job);
+	xe_vm_reactivate_rebind(vm);
 
 err_repin:
 	if (!xe_vm_no_dma_fences(vm))

drivers/gpu/drm/xe/xe_vm.c

@@ -226,6 +226,19 @@ static int wait_for_existing_preempt_fences(struct xe_vm *vm)
 	return 0;
 }
 
+static bool xe_vm_is_idle(struct xe_vm *vm)
+{
+	struct xe_engine *e;
+
+	xe_vm_assert_held(vm);
+	list_for_each_entry(e, &vm->preempt.engines, compute.link) {
+		if (!xe_engine_is_idle(e))
+			return false;
+	}
+
+	return true;
+}
+
 static void arm_preempt_fences(struct xe_vm *vm, struct list_head *list)
 {
 	struct list_head *link;
@@ -548,6 +561,11 @@ static void preempt_rebind_work_func(struct work_struct *w)
 	if (err)
 		goto out_unlock_outer;
 
+	if (xe_vm_is_idle(vm)) {
+		vm->preempt.rebind_deactivated = true;
+		goto out_unlock;
+	}
+
 	/* Fresh preempt fences already installed. Everyting is running. */
 	if (!preempt_fences_waiting(vm))
 		goto out_unlock;

drivers/gpu/drm/xe/xe_vm.h

@@ -98,6 +98,23 @@ extern struct ttm_device_funcs xe_ttm_funcs;
 
 struct ttm_buffer_object *xe_vm_ttm_bo(struct xe_vm *vm);
 
+/**
+ * xe_vm_reactivate_rebind() - Reactivate the rebind functionality on compute
+ * vms.
+ * @vm: The vm.
+ *
+ * If the rebind functionality on a compute vm was disabled due
+ * to nothing to execute. Reactivate it and run the rebind worker.
+ * This function should be called after submitting a batch to a compute vm.
+ */
+static inline void xe_vm_reactivate_rebind(struct xe_vm *vm)
+{
+	if (xe_vm_in_compute_mode(vm) && vm->preempt.rebind_deactivated) {
+		vm->preempt.rebind_deactivated = false;
+		queue_work(system_unbound_wq, &vm->preempt.rebind_work);
+	}
+}
+
 static inline bool xe_vma_is_userptr(struct xe_vma *vma)
 {
 	return !vma->bo;

drivers/gpu/drm/xe/xe_vm_types.h

@@ -293,6 +293,11 @@ struct xe_vm {
 		struct list_head engines;
 		/** @num_engines: number user engines attached to this VM */
 		int num_engines;
+		/**
+		 * @rebind_deactivated: Whether rebind has been temporarily deactivated
+		 * due to no work available. Protected by the vm resv.
+		 */
+		bool rebind_deactivated;
 		/**
 		 * @rebind_work: worker to rebind invalidated userptrs / evicted
 		 * BOs