# How to build and test Cloud Hypervisor on AArch64

This document introduces how to build and test Cloud Hypervisor on AArch64.
Currently, Cloud Hypervisor supports 2 methods of booting on AArch64: UEFI
booting and direct-kernel booting. The document covers both methods.

All the steps are based on Ubuntu. We use the Ubuntu cloud image for guest VM
disk.

## Hardware requirements

- AArch64 servers (recommended) or development boards equipped with the GICv3
interrupt controller.

- On development boards that have constrained RAM resources, if the creation of
a VM consumes a large portion of the free memory on the host, it may be required
to enable swap. For example, this was required on a board with 3 GB of RAM
booting a 2 GB VM at a point in time when 2.8 GB were free. Without enabling
swap the `cloud-hypervisor` process was terminated by the OOM killer. In this
situation memory was allocated for the virtual machine using memfd while the
page cache was filled, leading to a situation where the kernel could not even
drop caches. Making a small section of swap available (observably, 1 to 15 MB),
this situation can be resolved and the resulting memory footprint of
`cloud-hypervisor` is as expected.

## Getting started

We create a folder to build and run Cloud Hypervisor at `$HOME/cloud-hypervisor`

```shell
$ export CLOUDH=$HOME/cloud-hypervisor
$ mkdir $CLOUDH
```

## Prerequisites

You need to install some prerequisite packages to build and test Cloud Hypervisor.

### Tools

```bash
# Install rust tool chain
$ curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh
# Install the tools used for building guest kernel, EDK2 and converting guest disk
$ sudo apt-get update
$ sudo apt-get install git build-essential m4 bison flex uuid-dev qemu-utils
```

### Building Cloud Hypervisor

```bash
$ pushd $CLOUDH
$ git clone https://github.com/cloud-hypervisor/cloud-hypervisor.git
$ cd cloud-hypervisor
$ cargo build
$ popd
```

### Disk image

Download the Ubuntu cloud image and convert the image type.

```bash
$ pushd $CLOUDH
$ wget https://cloud-images.ubuntu.com/focal/current/focal-server-cloudimg-arm64.img
$ qemu-img convert -p -f qcow2 -O raw focal-server-cloudimg-arm64.img focal-server-cloudimg-arm64.raw
$ popd
```

## UEFI booting

This part introduces how to build EDK2 firmware and boot Cloud Hypervisor with it.

### Building EDK2

```bash
$ pushd $CLOUDH

# Clone source code repos
$ git clone --depth 1 https://github.com/tianocore/edk2.git -b master
$ cd edk2
$ git submodule update --init
$ cd ..
$ git clone --depth 1 https://github.com/tianocore/edk2-platforms.git -b master
$ git clone --depth 1 https://github.com/acpica/acpica.git -b master

# Build tools
$ export PACKAGES_PATH="$PWD/edk2:$PWD/edk2-platforms"
$ export IASL_PREFIX="$PWD/acpica/generate/unix/bin/"
$ make -C acpica
$ cd edk2/
$ . edksetup.sh
$ cd ..
$ make -C edk2/BaseTools

# Build EDK2
$ build -a AARCH64 -t GCC5 -p ArmVirtPkg/ArmVirtCloudHv.dsc -b RELEASE

$ popd
```

If the build goes well, the EDK2 binary is available at
`edk2/Build/ArmVirtCloudHv-AARCH64/RELEASE_GCC5/FV/CLOUDHV_EFI.fd`.

### Booting the guest VM

```bash
$ pushd $CLOUDH
$ sudo RUST_BACKTRACE=1 $CLOUDH/cloud-hypervisor/target/debug/cloud-hypervisor \
           --api-socket /tmp/cloud-hypervisor.sock \
           --kernel $CLOUDH/edk2/Build/ArmVirtCloudHv-AARCH64/RELEASE_GCC5/FV/CLOUDHV_EFI.fd \
           --disk path=$CLOUDH/focal-server-cloudimg-arm64.raw \
           --cpus boot=4 \
           --memory size=4096M \
           --net tap=,mac=12:34:56:78:90:01,ip=192.168.1.1,mask=255.255.255.0 \
           --serial tty \
           --console off
$ popd
```

## Direct-kernel booting

Alternativelly, you can build your own kernel for guest VM. This way, UEFI is
not involved and ACPI cannot be enabled.

### Building kernel

```bash
$ pushd $CLOUDH
$ git clone --depth 1 "https://github.com/cloud-hypervisor/linux.git" -b ch-5.12
$ cd linux
$ cp $CLOUDH/cloud-hypervisor/resources/linux-config-aarch64 .config
$ make -j `nproc`
$ popd
```

### Booting the guest VM

```bash
$ pushd $CLOUDH
$ sudo $CLOUDH/cloud-hypervisor/target/debug/cloud-hypervisor \
           --api-socket /tmp/cloud-hypervisor.sock \
           --kernel $CLOUDH/linux/arch/arm64/boot/Image \
           --disk path=focal-server-cloudimg-arm64.raw \
           --cmdline "keep_bootcon console=ttyAMA0 reboot=k panic=1 root=/dev/vda1 rw" \
           --cpus boot=4 \
           --memory size=4096M \
           --net tap=,mac=12:34:56:78:90:01,ip=192.168.1.1,mask=255.255.255.0 \
           --serial tty \
           --console off
$ popd
```