[RISC-V Architecture Training] @DEMO: QEMU full system emulator

riscv

QEMU

  • QEMU is a binary translating emulator
    • On-the-fly, translate RISC-V instruction to host CPU instruction (e.g. x86)
    • Functional, not accurate; but really fast
      • Good for software debugging, not for hardware debuggin
Type Example Performance
Functional QEMU 100 million to >1 billion instructions per second
Trace-accurate Spike 10 to 100 million instructions per second
Cycle-accurate Verilator/rocket-chip 10 to 100 thousand instructions per second

RISC-V boards

  • virt - priv v1.10 (16550A UART, virtio-net, virtio-block and device-tree)
  • spike_v1.9 - priv v1.9.1 (HTIF and config-string)
  • spike_v1.10 - priv v1.10 (HTIF and device-tree)
  • sifive_e300 - priv v1.10 (SiFiveUART, HiFive1 compatible)
  • sifive_u500 - priv v1.10 (SiFiveUART and device-tree)

VirtIO board

  • Implements VirtIO MMIO (memory mapped IO)
  • Supports VirtIO block devices, network devices, and UART
    • Full system with storage, neworking
    • Use PLIC as interrupt controller
  • Can boot Busybear Linux
  • Can boot Fedora Linux

Install QEMU

Install prerequisites

Need newer version GCC, so just installed gcc-8

apt-get install software-properties-common
add-apt-repository ppa:ubuntu-toolchain-r/test
apt-get update
apt-get install gcc-8 g++-8

Compile QEMU from source

git clone https://git.qemu.org/git/qemu.git
git submodule update --init --recursive

cd qemu
./configure --target-list=riscv64-softmmu && make

Run Freedom-E-SDK on QEMU

Run examples from Freedom IDE

Boot 64-bit Fedora on QEMU

Download Fedora 64-bit image for RISC-V

mkdir disk-images && cd disk-images
wget https://fedorapeople.org/groups/risc-v/disk-images/stage4-disk.img.xz
xzdec -d stage4-disk.img.xz > stage4-disk.img

# Berkeley bootloader
wget https://fedorapeople.org/groups/risc-v/disk-images/bbl

Boot Linux ~/riscv-git/qemu/run-qemu.sh

./riscv64-softmmu/qemu-system-riscv64 \
    -nographic \
    -machine virt \
    -smp 4 \
    -m 2G \
    -kernel ./disk-images/bbl \
    -object rng-random,filename=/dev/urandom,id=rng0 \
    -device virtio-rng-device,rng=rng0 \
    -append "console=ttyS0 ro root=/dev/vda" \
    -device virtio-blk-device,drive=hd0 \
    -drive file=./disk-images/stage4-disk.img,format=raw,id=hd0 \
    -device virtio-net-device,netdev=usernet \
    -netdev user,id=usernet,hostfwd=tcp::10000-:22

Login: root
Password: riscv

uname

[root@stage4 ~]# uname -a
Linux stage4.fedoraproject.org 4.19.0-rc8 #1 SMP Wed Oct 17 15:11:25 UTC 2018 riscv64 riscv64 riscv64 GNU/Linux
[root@stage4 ~]# cat /proc/cpuinfo
hart    : 0
isa     : rv64imafdcsu
mmu     : sv48

hart    : 1
isa     : rv64imafdcsu
mmu     : sv48

hart    : 2
isa     : rv64imafdcsu
mmu     : sv48

hart    : 3
isa     : rv64imafdcsu
mmu     : sv48

Hello world

[root@stage4 ~]# cat hello.c
#include <stdio.h>

int main(void) {
        printf("Hello world!\n");
}
[root@stage4 ~]# gcc hello.c -o hello
[root@stage4 ~]# ./hello
Hello world!

Size difference

  • In QEMU (with Linux)
-rwxr-xr-x 1 root root 7936 Jul  5 05:39 hello
  • With newlib
-rwxr-xr-x  1 jimw  1876110778     20880 Jul 22 09:07 hello.elf
  • 2.63x in size, because Linux version binary doesn’t include system call functions

Python

[root@stage4 ~]# python3
Python 3.6.4 (default, Mar 20 2018, 00:39:12)
[GCC 7.3.1 20180303 (Red Hat 7.3.1-5)] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import os
>>> os.uname()
posix.uname_result(sysname='Linux', nodename='stage4.fedoraproject.org', release='4.19.0-rc8', version='#1 SMP Wed Oct 17 15:11:25 UTC 2018', machine='riscv64')
>>> exit()