# Linux Kernel Module Cheat

### 23.1. Introduction to QEMU

QEMU is a system simulator: it simulates a CPU and devices such as interrupt handlers, timers, UART, screen, keyboard, etc.

If you are familiar with VirtualBox, then QEMU then basically does the same thing: it opens a "window" inside your desktop that can run an operating system inside your operating system.

Also both can use very similar techniques: either Binary translation or KVM. VirtualBox' binary translator is / was based on QEMU’s it seems: https://en.wikipedia.org/wiki/VirtualBox#Software-based_virtualization

The huge advantage of QEMU over VirtualBox is that is supports cross arch simulation, e.g. simulate an ARM guest on an x86 host.

QEMU is likely the leading cross arch system simulator as of 2018. It is even the default Android simulator that developers get with Android Studio 3 to develop apps without real hardware.

Another advantage of QEMU over virtual box is that it doesn’t have Oracle' hands all all over it, more like RedHat + ARM.

Another advantage of QEMU is that is has no nice configuration GUI. Because who needs GUIs when you have 50 million semi-documented CLI options? Android Studio adds a custom GUI configuration tool on top of it.

QEMU is also supported by Buildroot in-tree, see e.g.: https://github.com/buildroot/buildroot/blob/2018.05/configs/qemu_aarch64_virt_defconfig We however just build our own manually with build-qemu, as it gives more flexibility, and building QEMU is very easy!

All of this makes QEMU the natural choice of reference system simulator for this repo.