I currently have a RV32IMC core implementation based on FPGA and I want to boot an operating system on it but somehow I couldn't find any useful documentation about, • which extensions should I implement, • which modes should I implement, • what about virtual memories, memory controllers, memory instructions etc. • which csr's should I implement and also do I need to write a boot sequence from zero is there any source to answer these questions and some others? any help would be appreciated.

1. You probably need atomic extension for Linux 2. Everything else depends on OS you want to boot