事实证明我猜的有 8 分对：
It's just a parameter to let the Android OS know that it's running in an emulated environment as opposed to running natively on a physical device.
For example, the GPU stack has to be somehow emulated using a custom OpenGL driver (in this case `mesa3d`). There's software emulation (swiftshader) and host GPU mode (GLES).
For performance reasons when using the host GPU, the GLES commands from the guest have to be serialized and sent over a kernel pipe to the QEMU and to the host OS. The commands are deserialized on the host and executed on the physical host GPU through the Shader Translator library (taken from the Google ANGLE project). The Google's QEMU fork (aka Android Emulator) usually loads this library and then takes care of proper rendering, such that users can see the rendering output of the emulated OS properly inside the emulator window on the host machine. You can do the same for the docker, otherwise you'd have to implement some other trick to share the GPU. virtio-gpu is a Linux kernel facility that is meant to replace QEMU pipe in the future.
The high-level details of this OpenGL emulation mechanism are described here: https://android.googlesource.com/platform/external/qemu/+/ma
You can find the implementation of the QEMU OpenGL pipe mechanism here: https://cs.android.com/android/platform/superproject/+/maste
软解效率高是源于这一个项目：ANGLE (全称 Almost Native Graphics Layer Engine),
redriod 和 anbox 果然是同一路线的，，，啥都一样。只是一个 lxc 一个 docker 的区别而已，anbox 有桌面集成直接处理相关的部分，而 redriod 更偏向命令行 adb 呈现服务