应用处理器

So far we’ve talked about microcontrollers, such as the Arm Cortex-M series. These are typically small systems with very limited resources.

Larger systems with more resources are typically called application processors, built around processors such as the ARM Cortex-A or Intel Atom.

For simplicity we’ll just work with QEMU’s aarch64 ‘virt’ board.

  • Broadly speaking, microcontrollers don’t have an MMU or multiple levels of privilege (exception levels on Arm CPUs, rings on x86).
  • Application processors have more resources, and often run an operating system, instead of directly executing the target application on startup.
  • QEMU 支持针对每种架构模拟不同的机器或板级模型。“虚拟”开发板并不适用于任何特定的真实硬件，而是专为虚拟机设计的。
  • We will still address this board as bare-metal, as if we were writing an operating system.