Ports/riscv64

RISC-V

RISC-V is an open and free instruction set architecture (ISA). The RISC-V ISA specifications are licensed under a Creative Commons license (CC BY 4.0). Anyone could get the final versions of the user-level ISA specifications and drafts of the compressed and privileged ISA specifications.

Another key feature of the RISC-V architecture that it is scalable and allows multiple implementations. The minimal specification has the commands to store and load, jump and integer arithmetic. It supports the 32-, 64- and 128-bit register sizes: "RV32I, RV64I and RV128I" ("I" stands for integer). This Linux port runs on "RV64IMAFDC" or "RV64GC" ("G" == "IMAFD"):

• I - Integer and basic instructions
• M - Multiply and divide
• A - Atomic operations
• F - Single precision floating point
• D - Double precision floating point
• C - Compressed instructions

At this page one could find the latest information about ALT port status for the new platform - RISC-V (RV64GC). We're building it on the HiFive Unleashed board from SiFive.

Working plan

• The following Linux kernels have been bare metal tested on SiFive HiFive Unleashed:
  • 4.15
  • 4.19-rc2
  • 4.19.6 (image RPM, SRPM, git)

• BOOT methods:
  • Berkeley bootloader -- DONE
  • U-BOOT (link) -- DONE

• Sisyphus port -- IN PROGRESS
  1. Toolchain (see the status above) -- DONE
  2. Linux Kernel -- DONE
  3. X11 -- DONE
  4. Desktop Environments -- IN PROGRESS
• ALT image metaprofile -- IN PROGRESS
• Girar Builder -- IN PROGRESS
• QEMU image (see below) -- DONE

One could find the latest rootfs snapshot (Nov 2018) here. The RPM/SRPM repository at here.

QEMU

You've got to install QEMU with riscv64 support to run ALT RISC-V port on QEMU.

In case of the ALT x86_64 host system, for example: qemu-system-riscv-core.

These bits are needed:

• rootfs -- raw image or to build a new one there is a tgz packed version
• kernel for QEMU

After these steps are done it's time to run a kernel!

(one possibly needs to change paths to the kernel and rootfs according to a particular system)

 qemu-system-riscv64 \
  -nographic -machine virt -kernel /boot/vmlinux-4.19.6-un-def-alt3 \
  -drive file=rootfs.raw,format=raw,id=hd0 -device virtio-blk-device,drive=hd0 \
  -append "earlyprintk root=/dev/vda rootwait fastboot console=ttyS0 debug sunrpc.debug STOP=udev" \
  -netdev user,id=eth0 -device virtio-net-device,netdev=eth0

To log into the shell: Username: root Password: 123

Useful links:

• Berkeley bootloader utils to merge the linux kernel into the bbl.bin with dummy payload.
• RISC-V specifications
• All Aboard -- cool series of blog posts by Palmer Dabbelt about RISC-V, toolchain, etc.
• OSSDEVCONF-2018 (in Russian)