What do VMs mean in this context?

I did a pass of the codebase and it seems they’re just forking processes?

It’s unclear to me where the safety guarantees come from (compared to using e.g. KVM).

Edit: it appears the safety guarantees come from libriscv[0]. As far as I can tell, these sandboxes are essentially RISC-V programs running in an isolated context (“machine”) where all the Linux syscalls are emulated and thus “safe.” Still curious what potential attack vectors may exist?

[0] https://github.com/libriscv/libriscv/tree/dfb7c85d01f01cb38f...