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qemu.md

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Running RISC-V based VM with qemu

This document discusses multiple ways qemu can be used to run a RISC-V virtual machine.

Based on the Instructions from RISC-V's Website

These instructions are taken from here, but some of them did not work as it is for me, and thus, they might be modified slightly. Moreover, these instructions do not build a disk image to be used with qemu, but relies on a busybox image.

First install pre-requisite libraries:

sudo apt install autoconf automake autotools-dev curl libmpc-dev libmpfr-dev libgmp-dev \
                 gawk build-essential bison flex texinfo gperf libtool patchutils bc \
                 zlib1g-dev libexpat-dev git

To install qemu itself for RISC-V, first set the $INSTALL_DIR to whatever path you want qemu to be installed in and then follow

git clone https://github.com/qemu/qemu
cd qemu
git checkout v5.0.0
./configure --target-list=riscv64-softmmu --prefix=$INSTALL_DIR
make -j $(nproc)
sudo make install

Compile Linux kernel (e.g. v5.4) for RISC-V:

git clone https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
cd linux
git checkout v5.4
make ARCH=riscv CROSS_COMPILE=riscv64-linux-gnu- defconfig
make ARCH=riscv CROSS_COMPILE=riscv64-linux-gnu- -j $(nproc)

To build busybox (binary containing many UNIX utilities) for RISC-V:

git clone https://git.busybox.net/busybox
cd busybox
CROSS_COMPILE=riscv64-linux-gnu- make defconfig
CROSS_COMPILE=riscv64-linux-gnu- make -j $(nproc)

Then to run qemu:

$INSTALL_DIR/bin/qemu-system-riscv64 -kernel linux/arch/riscv/boot/Image -append "root=/dev/vda ro console=ttyS0" -drive file=busybox/busybox,format=raw,id=hd0 -device virtio-blk-device,drive=hd0

Based on the Instructions from Debian's Website

These instructions are based on the documentation of Debian port for RISC-V.

Follow the same instructions as above to build qemu and Linux kernel for RISC-V.

Next, install the required libraries:

sudo apt-get install debootstrap qemu-user-static binfmt-support debian-ports-archive-keyring

We also need to update the package sources to be able to access debian-ports repository. Do the following:

vim  /etc/apt/sources.list

Add the following in /etc/apt/sources.list:

deb http://ftp.ports.debian.org/debian-ports unstable main

And run:

apt-get update

If you see an error about key expiration, run :

sudo apt-key adv --keyserver keys.gnupg.net --recv-keys [expired key]

Or

sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys [expired key]

Next, we need to create a riscv chroot (operation that changes the apparent root directory of the current running process) using debootstrap tool.

Use the following command to that (this will create a chroot in /tmp/riscv64-chroot):

sudo debootstrap --arch=riscv64 --foreign --variant=buildd  --keyring /usr/share/keyrings/debian-ports-archive-keyring.gpg --include=debian-ports-archive-keyring unstable /tmp/riscv64-chroot http://deb.debian.org/debian-ports

Some further processing is needed to prepare this chroot to be used as the base of the virtual machine.

qemu-static for RISC-V is needed to be able to update packages (or run RISC-V specific applications) inside the file-system of the qemu disk image (virtual machine) from the host, once we chroot to the RISC-V debian file-system.

To install qemu-static in chroot:

cat >/tmp/qemu-riscv64 <<EOF
package qemu-user-static
type magic
offset 0
magic \x7f\x45\x4c\x46\x02\x01\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\x02\x00\xf3\x00
mask \xff\xff\xff\xff\xff\xff\xff\x00\xff\xff\xff\xff\xff\xff\xff\xff\xfe\xff\xff\xff
interpreter /usr/bin/qemu-riscv64-static
EOF

OR (assuming that qemu-riscv64 is installed on the system)

sudo cp /usr/bin/qemu-riscv64-static /tmp/riscv64-chroot/usr/bin/
sudo update-binfmts --import /tmp/qemu-riscv64

Also copy the previously built Linux image to inside the debain chroot:

[path to the linux source folder]/linux/arch/riscv/boot/Image /tmp/riscv64-chroot/boot/

This is needed as we will see in the later part when qemu is started.

Then run chroot on the previously created directory:

sudo chroot /tmp/riscv64-chroot

Then inside the chroot, to prepare the virtual machine:

apt-get update

To set-up networking inside the VM:

cat >>/etc/network/interfaces <<EOF
auto lo
iface lo inet loopback

auto eth0
iface eth0 inet dhcp
EOF
# Set root password
passwd
# Disable the getty on hvc0 as hvc0 and ttyS0 share the same console device in qemu.
ln -sf /dev/null /etc/systemd/system/[email protected]
# Install kernel and bootloader infrastructure
apt-get install linux-image-riscv64 u-boot-menu
# Install and configure ntp tools
apt-get install openntpd ntpdate
sed -i 's/^DAEMON_OPTS="/DAEMON_OPTS="-s /' /etc/default/openntpd
# Configure syslinux-style boot menu
cat >>/etc/default/u-boot <<EOF
U_BOOT_PARAMETERS="rw noquiet root=/dev/vda1"
U_BOOT_FDT_DIR="noexist"
EOF

This tutorial uses u-boot as the bootloader. To generate the menu files used by u-boot in the chroot directory, run:

apt-get install u-boot-menu
u-boot-update

To exit the chroot:

exit

Create disk image rootfs.img from previous chroot directory:

sudo apt-get install libguestfs-tools
sudo virt-make-fs --partition=gpt --type=ext4 --size=10G /tmp/riscv64-chroot/ rootfs.img
sudo chown ${USER} rootfs.img

Then run qemu with this disk image:

$INSTALL_DIR/bin/qemu-system-riscv64 -nographic -machine virt -m 1.9G -kernel /usr/lib/riscv64-linux-gnu/opensbi/generic/fw_jump.elf -device loader,file=/usr/lib/u-boot/qemu-riscv64_smode/uboot.elf -object rng-random,filename=/dev/urandom,id=rng0 -device virtio-rng-device,rng=rng0 -append "console=ttyS0 rw root=/dev/vda1" -device virtio-blk-device,drive=hd0 -drive file=rootfs.img,format=raw,id=hd0 -device virtio-net-device,netdev=usernet -netdev user,id=usernet,hostfwd=tcp::22222-:22

Running the above command shows the following error and fall back to OpenSBI:

TFTP error: 'Access violation' (2)
Not retrying...
BOOTP broadcast 1
DHCP client bound to address 10.0.2.15 (0 ms)
Using virtio-net#2 device
TFTP from server 10.0.2.2; our IP address is 10.0.2.15
Filename 'boot.scr.uimg'.
Load address: 0x81000000
Loading: *
TFTP error: 'Access violation' (2)
Not retrying...

However, the kernel booting process can be continued from this point by running the following (reference):

load virtio 0:1 ${kernel_addr_r} /boot/Image
booti ${kernel_addr_r} - ${fdtcontroladdr}

Booting Ubuntu RISCV With qemu:

There are some cloud images provided here for different Ubuntu versions with RISC-V and instructions to use them with qemu are here.