Machine privilege level was specially designed to use in vendor's
firmware or bootloader. We have implemented operation in machine
mode in FreeBSD as part of understanding RISC-V ISA, but it is time
to remove it.
We now use BBL (Berkeley Boot Loader) -- standard RISC-V firmware,
which provides operation in machine mode for us.
We now use standard SBI calls to machine mode, instead of handmade
'syscalls'.
o Remove HTIF bus.
HTIF bus is now legacy and no longer exists in RISC-V specification.
HTIF code still exists in Spike simulator, but BBL do not provide
raw interface to it.
Memory disk is only choice for now to have multiuser booted in Spike,
until Spike has implemented more devices (e.g. Virtio, etc).
Sponsored by: DARPA, AFRL
Sponsored by: HEIF5
Tested on Spike simulator with 2 and 16 cores (tlb enabled),
so set MAXCPU to 16 at this time.
This uses FDT data to get information about CPUs
(code based on arm64 mp_machdep).
Invalidate entire TLB cache as it is the only way yet.
Sponsored by: DARPA, AFRL
Sponsored by: HEIF5
o Add kernel configuration for QEMU.
Both SPIKE and QEMU kernel configs are temporary (until
we will be able to obtain DTB from loader).
Sponsored by: DARPA, AFRL
Sponsored by: HEIF5
This is the final step required allowing to compile and to run RISC-V
kernel and userland from HEAD.
RISC-V is a completely open ISA that is freely available to academia
and industry.
Thanks to all the people involved! Special thanks to Andrew Turner,
David Chisnall, Ed Maste, Konstantin Belousov, John Baldwin and
Arun Thomas for their help.
Thanks to Robert Watson for organizing this project.
This project sponsored by UK Higher Education Innovation Fund (HEIF5) and
DARPA CTSRD project at the University of Cambridge Computer Laboratory.
FreeBSD/RISC-V project home: https://wiki.freebsd.org/riscv
Reviewed by: andrew, emaste, kib
Relnotes: Yes
Sponsored by: DARPA, AFRL
Sponsored by: HEIF5
Differential Revision: https://reviews.freebsd.org/D4982
