This document provides instructions to create the “riscv-ubuntu” image and points to the gem5 component that would work with the disk image. The riscv-ubuntu disk image is based on Ubuntu's preinstalled server image for RISC-V SiFive HiFive Unmatched available at (https://cdimage.ubuntu.com/releases/20.04.3/release/). The .bashrc file would be modified in such a way that it executes a script passed from the gem5 configuration files (using the m5 readfile instruction).
We assume the following directory structure while following the instructions in this README file:
riscv-ubuntu/ |___ gem5/ # gem5 source code (to be cloned here) | |___ riscv-gnu-toolchain/ | |___ qemu/ | |___ disk-image/ | |___ ubuntu.img # The ubuntu disk image should be downloaded and modified here | |___ shared/ # Auxiliary files needed for disk creation | | |___ serial-getty@.service # Auto-login script | |___ riscv-ubuntu/ | |___ gem5_init.sh # The script to be appended to .bashrc on the disk image | |___ post-installation.sh # The script manipulating the disk image | |___ riscv-ubuntu.json # The Packer script | |___ exit.sh # A script that calls m5 exit | | |___ README.md # This README file
# Install QEMU dependencies sudo apt-get install ninja-build cd riscv-ubuntu/ # QEMU git clone https://github.com/qemu/qemu --recursive cd qemu git checkout 0021c4765a6b83e5b09409b75d50c6caaa6971b9 ./configure --target-list=riscv64-softmmu make -j $(nproc) make install cd .. # RISCV toolchain git clone https://github.com/riscv-collab/riscv-gnu-toolchain --recursive cd riscv-gnu-toolchain git checkout 1a36b5dc44d71ab6a583db5f4f0062c2a4ad963b # --prefix parameter specifying the installation location ./configure --prefix=/opt/riscv make linux -j $(nproc) cd ..
There are more versions of Ubuntu that are supported for RISCV, they are available at (https://wiki.ubuntu.com/RISC-V). In the following command, we will use the Ubuntu 20.04.4 disk image.
# downloading the disk image wget https://cdimage.ubuntu.com/releases/20.04.3/release/ubuntu-20.04.4-preinstalled-server-riscv64+unmatched.img.xz # unpacking/decompressing the disk image xz -dk ubuntu-20.04.4-preinstalled-server-riscv64+unmatched.img.xz # renaming the disk image mv ubuntu-20.04.4-preinstalled-server-riscv64+unmatched.img ubuntu.img # adding 4GB to the disk qemu-img resize -f raw ubuntu.img +4G
According to (https://wiki.ubuntu.com/RISC-V),
Prerequisites:
apt install qemu-system-misc opensbi u-boot-qemu qemu-utils
u-boot-qemu version 2022.01 (or newer) is required to boot in qemu.
To use this version of u-boot-qemu, we will download the package from here, (https://mirrors.edge.kernel.org/ubuntu/pool/main/u/u-boot/). The following command will download and install the package.
wget https://mirrors.edge.kernel.org/ubuntu/pool/main/u/u-boot/u-boot-qemu_2022.01%2Bdfsg-2ubuntu2_all.deb dpkg -i u-boot-qemu_2022.01+dfsg-2ubuntu2_all.deb apt-get install -f
The correct version of u-boot-qemu is also available in the Ubuntu 22.04 or later.
apt install u-boot-qemu
The following command will install the rest of the dependencies,
apt install qemu-system-misc opensbi qemu-utils
# Within the `src/riscv-ubuntu` directory. git clone https://gem5.googlesource.com/public/gem5 cd gem5/util/m5 scons build/riscv/out/m5 cd ../../..
Note: the default cross-compiler is riscv64-unknown-linux-gnu-. To change the cross-compiler, you can set the cross-compiler using the scons sticky variable riscv.CROSS_COMPILE. For example,
scons riscv.CROSS_COMPILE=riscv64-linux-gnu- build/riscv/out/m5
The following qemu command will boot the system using the disk image and the bootloader downloaded earlier.
./qemu/build/qemu-system-riscv64 -machine virt -nographic \ -m 16384 -smp 8 \ -bios /usr/lib/riscv64-linux-gnu/opensbi/generic/fw_jump.elf \ -kernel /usr/lib/u-boot/qemu-riscv64_smode/uboot.elf \ -device virtio-net-device,netdev=eth0 \ -netdev user,id=eth0,hostfwd=tcp::5555-:22 \ -drive file=ubuntu.img,format=raw,if=virtio
Note: the above command will forward the guest‘s port 22 to the host’s port 5555. This is done so that we can transfer and install benchmarks to the guest system from the host via SSH (facilitated by Packer).
On the first boot, the guest OS will ask to input username and password. The default username and password is,
Username: ubuntu Password: ubuntu
After changing the password and login to the guest OS, you can stop cloud-init and launch the SSH server,
sudo touch /etc/cloud/cloud-init.disabled # stop cloud-init /etc/init.d/ssh start # start the SSH server sudo apt-get update sudo apt-get upgrade
The disk image can be built using (Packer)[https://www.packer.io/].
While the qemu instance is still running, we will use Packer to connect to the virtual machine and manipulate the disk image.
cd riscv-ubuntu/ scp -P 5555 gem5/util/m5/build/riscv/out/m5 ubuntu@localhost:/home/ubuntu/ scp -P 5555 disk-image/shared/serial-getty@.service ubuntu@localhost:/home/ubuntu/ scp -P 5555 disk-image/riscv-ubuntu/gem5_init.sh ubuntu@localhost:/home/ubuntu/ scp -P 5555 disk-image/riscv-ubuntu/exit.sh ubuntu@localhost:/home/ubuntu/
Connecting to the guest,
ssh -p 5555 ubuntu@localhost
In the guest,
sudo -i # input password mv /home/ubuntu/serial-getty@.service /lib/systemd/system/ mv /home/ubuntu/m5 /sbin ln -s /sbin/m5 /sbin/gem5 mv /home/ubuntu/gem5_init.sh /root/ chmod +x /root/gem5_init.sh echo "/root/gem5_init.sh" >> /root/.bashrc mv /home/ubuntu/exit.sh /root/ chmod +x /root/exit.sh
A pre-build, gzipped, disk image is available at http://dist.gem5.org/dist/v22-1/images/riscv/ubuntu-20-04/riscv-ubuntu-20220318.img.gz. Note: The password set for the ubuntu user is helloworld.
This disk image is used in the following gem5 example RISCV config files, found within the gem5 repository:
gem5/configs/example/gem5_library/riscv-fs.py, which simulates a full system running with RISCV ISA.gem5/configs/example/gem5_library/riscv-ubuntu-run.py, which simulates a full system with RISCV based Ubuntu 20.04 disk-image. Upon successful start-up, a m5_exit instruction encountered is encountered. The simulation ends then.Note: To use the locally built Ubuntu image in gem5, make sure to pass the root_partition parameter to CustomResource or CustomDiskImageResource. For example,
board.set_kernel_disk_workload( kernel=Resource("riscv-bootloader-vmlinux-5.10"), disk_image=CustomDiskImageResource( local_path="<RESOURCES_PARENT_PATH>/gem5-resources/src/riscv-ubuntu/ubuntu.img", disk_root_partition="1", ) )