WordPress is so cumbersome (brut long text in SQL DB and other misconception (WTF?), buggy (especially to multilingual content missing) and hard to maintain on long term that I didn’t posted for long time I want to migrate. You can test the new log engine (here specialised in TIC-80 256 bytes code on https://256b.popolon.org/.

I continued my travel toward RISC-V I started as said in a previous post in may 2018.

RISC-V Benefits

Among the benefit of RISC-V beside other implementations:
* Open source and without license fee availability, allowing everyone to participate, implement and have full specifications
* Highest modularity for a processor in specifications, You can reduce the core to only the set of functions you want for a specific tasks, allowing less transistor/more compact specialized cores, and then multiply cores with some specialized in some kind of tasks.
* Vector extension

As example of specific task oriented cores:
* You don’t need a SIMD if you have a more powerful DSP unit, and you can implement this DSP unit using a RISC-V core with Vector extension, that is more efficient that a simple SIMD for this kind of task.
* JIT extension could be useful for some dynamic web server using scripting language (as PHP, Ruby, JS), but less useful for static web server (PCRE-jit computation in servers like nginx is marginal a core could be dedicated on a processor with many cores without this extension). Alibaba Group (Chinese Amazon) developed it’s own RISC-V implementation for its web servers).
* The European processor Initiative started in 2018, with first goal to uses United Kingdom made ARM core for main processor (at this time ARM had solid build/compilation/system ecosystem) with several kind of computing accelerators based on RISC-V, called EPAC (European Processor Accelerators)(a.is). It is developed at Barcelone with several partners inside European Union(a.is), Sadly as most European union project it will help USA industry for manufacturing, (GlobalFoundries) instead of maintain, sustain and develop local knowledge, experience and workforce for independence, employment and smaller carbon footprint shipments (as China and United-States do). The first test version is a 22nm FPGA, the production one will be 12nm ASIC, and among the objectives, there will be to highest throughput while not going above the 1GHz top barrier, to achieve higher energy efficiency.

Operating System working on RISC-V in June 2021

First efforts with toward embedded operating systems as first available RISC-V chips was in this domain. As the RISC-V embedded market is mature, more effort are made toward mobile and desktop Operating Systems.

Several Linux distribution already work on RISC-V now. Next Debian Bulleye (release August 14 2021, already in beta), Fedora have a RISC-V flavor already working on the BeagleV Starlight open-source board and its StarFive JH7100 processor, and there is a port of Yocto.

For reference, here is instructions about making the RISCV64 virtual machine on Debian Wiki, and a more general guide to make Linux run on Qemu, RISC-V.

You can find the Debian RISC-V system image on this page, just click on to download (direct link). This image is made with Debian Quick Image Baker (dqib)

To run it, you also need OpenSBI (Open Source Supervisor Binary Interface) needed to load the bootloader (Documentation, Prebuild deb packages) I used deb package on Archlinux:

ar x ../opensbi_0.9-1_all.deb
SBIPATH=`pwd`
(cd /; sudo tar xf "$SBIPATH/data.tar.xz")

And the Uboot for Qemu. I personally just extract and the directory that also contain, the “artifacts” Debian image.

By default image is in Qcow format, that is more compact for unused blocks, but also really slower.
You can convert it easily by:

qemu-img convert -f qcow2 -O raw image.qcow2 image.raw

Here is the boot.sh to launch it (you can replace image.raw by image.qcow2, if you have a verypowerfull system and only place count: I use 2 cores and 512M of RAM. For huge compilation I restart it with more mem (1536M is generally enough, but more means more cache and faster compilation).

cores=2
mem=512M
qemu-system-riscv64 -machine virt -cpu rv64 -smp ${cores} -m ${mem} \
  -device virtio-blk-device,drive=hd -drive file=image.raw,if=none,id=hd \
  -device virtio-net-device,netdev=net -netdev user,id=net,hostfwd=tcp::2222-:22 \
  -bios /usr/riscv64-linux-gnu/lib/opensbi/generic/fw_jump.elf \
  -kernel ../qemu-riscv64_smode/uboot.elf \
  -object rng-random,filename=/dev/urandom,id=rng -device virtio-rng-device,rng=rng \
  -nographic -append "root=LABEL=rootfs console=ttyS0"

The login/pass are root/root.

you can connect by ssh:

ssh -p 2222 root@127.0.0.1

and rsync files via:

rsync -a --rsh="ssh -p 2222" root@127.0.0.1:path/to/rsync .

I already managed to compile TIC-80 on it and run it on Qemu:

.

There is also BareDOOM a port of DOOM that run on RISC-V emulated in TinyEmu (source code in the same page, there is also a fork with additional features on GitHub, a system emulator for the RISC-V and x86 architectures), JSLinux allow to run it in a browser (There is also a Quake port on RISC-V K210 microcontroller based Sipeed Maix Bit board). There is also a patched version of buildroot for K210 (no-mmu), for building Linux on this platform.

There is an important Note in system images from Fabrice Bellard site to make binary working with TinyEMU:

- TinyEMU only supports raw boot loader and kernel images. So after
  building riscv-pk or the Linux kernel, you must convert the ELF
  image to a raw image with:

  riscv64-unknown-linux-gnu-objcopy -O binary bbl bbl.bin
  
  riscv64-unknown-linux-gnu-objcopy -O binary vmlinux kernel.bin

A port of Haiku has already well progressed, also use TinyEMU for the port.

Update 2 July 2021: Another RISC-V (RV32 only) emulator is Nemu (github) it is a part of XiangShan (香山) RISC-V open processor from Chinese Academy of Sciences (OpenXiangShan (Gitee)) made by Chinese Academy of Sciences, the processors should have the performances of an ARM Cortex-A72/A73 in july 2021 with a 28nm process in first batch (Yanqi hu / Yanqi Lake / 雁栖湖), and performances of an Intel i9-10900K in second batch ( Nanhu / South Lake / 南湖) in fall 2021, with 14nm process, both manufactured by TSMC, and it already run GNU/Linux distribution Debian. See also(中文).

Another Virtual Machine emulator for RISC-V is JuiceVM supporting RV64IMASU. It is lightweight, support small UART serial I/O and MMU

Available RISC-V Hardware in June 2021

Several developers have received a first beta version of BeagleV RISC-V board. Here are demos (on youtube sadly) of first tries of different devs at beginning of may "BeagleV RISC-V Computer (Beta)" (unboxing), "BeagleV from BeagleBoard.org Fedora image Live Booting - 1" (booting), now BeagleV give a prepared Fedora with XFCE working on HDMI.

I have now 2 embedded microcontroller oriented RISC-V Board from Sipeed, one 32bits and one MaixDuino SipeedM1 (microPython (by default), dual-core 64bits+AI module) of the young hackers, Shenzhen based, SiPeed company. The last one support lot of embedded systems including default MicroPython based MaixDuino system (and cool plateforrm.io interface, Arduino, PlatformIO, microPython, OpenMV, FreeRTOS, et TensorFlow, etc..

The Nezha board of SiPeed, is a bit more expansive and with lower specs in first version, but very promising for the future Nezha: Your first RV64 Linux SBC for IoT~ (video Youtube).

Huawei Hi3861 is oriented toward their LiteOS kernel that is used in their new Android compatible HarmonyOS.

The BL602/BL604 de Bouffalo Lab (RISC-V WiFi & Bluetooth 5.0 LE) based on ESP32-C (RISC-V variant of ESP32, pin2pin compatible) is a 100 % open source BootLoader & driver (no blob needed), thanks to the work of Lup Yuen Lee (李立源). He wrote lot of interesting articles about the process of making the driver and a book about this chip, and several article around Ecosystem, including using Rust, How to simulate it in WebAssembly, etc.

China Science Academy is currently working on optimizing Firefox (SpiderMonkey) and Chrome/ium (Webkit) engines for RISC-V 2000 laptops with equivalent power of a Cartex-A78 should be available at then end of 2022

At the same time the port of true GNU/Linux on embedded devices like phones progress fast, on ARM architecture, with specialized distributions like PostMarket OS (and it's derivative Alpine Linux), or more general distributions, including Debian, Manjaro (ArchLinux derivative) etc. Port of KDE Plasma and GTK4/GNOME40 (especially GTK4.1+ with very efficient OpenGL acceleration, are of great help in this area. PinePhone from Pine64.org community is really an active and efficient hub for these ports. This phone (developer oriented in current state) is at the same time cheap (<200€) have hard switch for all network features, and every part can be easily changed. Those project are all ready to be ported on RISC-V versions of this kind of devices. Pine64 is already working on RISC-V opensource bl602 driver (see above) and a RISC-V (GD32VF103TB) running a smart/programmable iron solderer, and a future RISC-V based mother board to replace the current ARM one on the PinePhone could be totally realistic. See also LINux on MOBile for news on the port of Linux on Mobile devices.

An interesting post (and blog) about RISC-V assembly programming from Stephen Marz, another blog about RISC-V assembly from Daniel Mangun and one from ieee.org Build a RISC-V CPU From Scratch. A simple HelloWorld example, with deep explanations, including Linux RISC-V Application Binary Interface (ABI), to start with RISC-V assembly, based on GNU Assembler (support RV32 & RV64). There is also a Python made, limited, RISC-V assembler. A complete tutorial in French for starting with the Sipeed Longan Nano, (available for ~5 € with LCD screen).

Update: see also the very interesting Bronzebeard assembler + bare-metal environment in a newer arcticle. And an article about bare-metal RISC-V Development with the GD32VF103CB.

HTML5 RISC-V Interpreter/simulator. There is also RARS a really slow/unusable Java RISC-V simulator (pacaur -S rars), jupiter (with link to other simulators) (pacaur -S jupiter) is another one, and spike (pacman -S spike) is a c made simulator. Ripes (pacaur -S ripes-git) is a very advanced one, with multiple level of pipe, data/instruction cache states, etc... Venus with online simulator in Kotlin language.

Tutorial serie about designing RISC-V processor in VHDL.

I hope that with progress I made in real-time programming and different new programming languages in last few years (Lua, some bit of RISC-V assembly, JavaScript), I will make quickly some RISC-V demo on embedded board.