# TYPE\_CPU

Qemu中所有CPU类型都有一个父类TYPE\_CPU。所以研究这个结构是开展后续研究的基础。

## 继承关系

按照老规矩，我们还是先看一下类型的继承层次关系。

```
  TYPE_OBJECT
  +-------------------------------+
  |class_init                     | = object_class_init
  |                               |
  |instance_size                  | = sizeof(Object)
  +-------------------------------+


  TYPE_DEVICE
  +-------------------------------+
  |class_size                     | = sizeof(DeviceClass)
  |class_init                     | = device_class_init
  |                               |
  |instance_size                  | = sizeof(Object)
  |instance_init                  | = device_initfn
  |instance_finalize              | = device_finalize
  |                               |
  |realize                        | = cpu_common_realizefn
  +-------------------------------+


  TYPE_CPU
  +-------------------------------+
  |class_size                     | = sizeof(CPUClass)
  |class_init                     | = cpu_class_init
  |                               |
  |instance_size                  | = sizeof(CPUState)
  |instance_init                  | = cpu_common_initfn
  |instance_finalize              | = cpu_common_finalize
  +-------------------------------+
```

可以看到，TYPE\_CPU是TYPE\_DEVICE的子类，也就是CPU类型的初始化遵从[Device类型初始化的方法](/understanding_qemu/00-devices/04-deviceclass_instance.md)。

大家可以看到realize函数也被我着重标出了。

## 初始化

针对TYPE\_CPU，我们能看到的初始化过程就是普通的类型初始化的流程，以及Device类型realize时所做的工作。

具体的工作流程将根据不同的CPU类型而有所不同，还需要按照不同的CPU和Machine类型来处理。


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