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Tackling RISC-V as a beginner at osdev

Posted: Thu Jul 03, 2025 7:28 am
by pearmypie
Hello and thank you in advance to anyone reading my post :)

To preface, I am an employed junior programmer, not a complete beginner.

I've read through the code of xv6-riscv and I've been wondering how I could approach making a basic OS for RISC-V that would run on qemu's "virt" machine.

My goals are to implement a simple OS with drivers for PS/2 keyboards and mice, video output (not just serial console) and disk storage. My timeframe is about 13 months to do this.

I've investigated the boot process and it seems pretty straightforward, but there aren't any "wiki-like" examples and sources that I could find in regards to OSDev.

My questions are as follows:
Should I do without U-Boot? Loading my kernel using `-kernel mykernel.elf` is very straightforward and I am sure I have access to all OpenSBI BIOS-like functions.

On the contrary, should I use the U-Boot SPL -> OpenSBI -> U-Boot sequence? As I understand, it implements a subset of UEFI. Is this a big advantage?

I greatly appreciate all advice.

Re: Tackling RISC-V as a beginner at osdev

Posted: Thu Jul 03, 2025 7:20 pm
by Octocontrabass
The advantage of U-Boot and its subset UEFI implementation is that it works the same way on lots of different hardware. If you want to see your OS running on bare metal, that's probably the best way to go.

For something that only needs to work in QEMU, U-Boot is probably not worth the trouble. You can always switch to using U-Boot later.