RVVM - The RISC-V Virtual Machine

RISC-V CPU & System software implementation written in С

What's working

• OpenSBI, custom firmwares boot and execute properly
• Linux kernel boots!
• Linux userspace works, interactive shell through UART
• Framebuffer graphics, working Xorg with mouse & keyboard
• Raw image mounted as rootfs

What's done so far

• Feature-complete RV32I instruction set
• C, M, A instruction extensions
• Extendable and fast instruction decoder
• Physical memory
• Memory mapping unit (MMU) with SV32 virtual addressing
• TLB address caching (greatly speeds up memory operations)
• MMIO handlers
• CSR operations
• UART 16550a-compatible text console
• Bootrom loading
• DTB loading, passing to firmware/kernel
• ELF kernel loading
• Interrupts
• PLIC/CLIC, timers
• PS2 Altera Controller, PS2 keyboard & mouse
• Graphical framebuffer
• ATA PIO hard drive
• OpenCores Ethernet
• [Somewhat WIP] Flash, RV64 CPU, JIT prototype

Usage

Currently builds using GNU Make and tested on Linux, Windows and MacOS systems. More build targets are going to be supported.

git clone https://github.com/LekKit/RVVM
cd RVVM
make
cd release.linux.x86_64

To cross-compile, pass CC=target-gcc and OS=target-os if the target OS differs from your host to make. You can configure the build with use flags

Examples:

make CC=x86_64-w64-mingw32-gcc OS=windows
make CC=aarch64-linux-gnu-gcc OS=linux USE_FB=0 USE_NET=1

Running:

./rvvm_x86_64 bootrom.bin -dtb=device.dtb -image=rootfs.img

The bootrom.bin file is a user-provided raw binary, loaded at 0x80000000 address where it starts execution, and device.dtb is a DTB file containing description of the machine. You can pass -image=rootfs.img to mount a raw partition image as a flash drive.

Our team

• LekKit: Instruction decoding, RAM/MMU/TLB implementation, RV32/64ICMA ISA, interrupts & timer, privileged ISA, JIT, lots of fixes
• Mr0maks: Initial ideas, C/M extensions, VM debugger, CSR work, NS16550A UART
• cerg2010cerg2010: ELF loading, important fixes, initial RV64 work, PLIC, PS2, ATA, Ethernet, XCB window backend
• Hoping to see more contributors here

TODO

• Debug the available functionality and make sure it's conforming to the specs
• Proper MMU atomicity, fence, native AMO
• Multicore support (already works but the kernel races and crashes sometimes)
• Improve MMU & TLB, allow their usage from JIT'ed code
• Floating-point extensions
• RV64-only instructions & MMU
• Integrate JIT into the VM
• Networking, sound?
• Other peripherals
• DTB generation
• A lot more...
• Userspace emulation?