Background: I'm using QEMU to virtualize xv6-riscv on top of WSL2. I'm looking to create some sort of clean OS shutdown process reminiscent of Linux's exit command. Currently I'm using Ctrl-a x to kill qemu, but I want to be able to do this programmatically from within the OS.
I know that the Linux exit command simply closes the current shell, which means I need a kernelspace way of detecting if there's any active shells left and a way of signalling to QEMU that it's turning off. I have full access to the kernel for recompiling, but I can't use external C libraries because there are none. Any solution I develop has to be basically from-scratch.
Thus, my question: What does an operating system need to do to tell a RISC-V QEMU instance that it's turning off? How do you exit QEMU itself from within the OS? This second point is important specifically because I'm instantiating QEMU from a Makefile in a CLI, and I'd like to have access to the terminal after the OS terminates, rather than have QEMU sitting there emulating a RISC-V with nothing on it.
note: This question is different from this other one because I'm asking about a guest OS initiated shutdown rather than a host initiated ACPI shutdown, as well as diving much deeper into the internals of QEMU and operating systems in general.
