Creating an aarch64 VM for qemuhost, with Arch Linux guest

Arch-aarch-qemu

/* 
 * This document is provided to the public domain under the 
 * terms of the WTFPL license.
 */
 
This is 
 
This is a combination of
 - [How to boot Arch Linux ARM in QEMU (patched for M1)](https://gist.github.com/thalamus/561d028ff5b66310fac1224f3d023c12) - thanks to  Avatar
Will Tisdale 
 - [How to launch ARM aarch64 VM with QEMU from scratch. ](https://futurewei-cloud.github.io/ARM-Datacenter/qemu/how-to-launch-aarch64-vm/) - thanks to Rob Foley
slightly adapted to Arch Linux.

0) Prerequisites
 * packages `qemu`, `qemu-arch-extra`, `multipath-tools` (for `kpartx`)
 * aur package `edk2-avmf`, which provides the firmware for aarch64
 * [ArchLinuxARM image for generic aarch64](https://archlinuxarm.org/platforms/armv8/generic)

1) Create the root image
 * Create the two flash images:
```bash
 ~ dd if=/dev/zero of=flash1.img bs=1M count=64
 ~ dd if=/dev/zero of=flash0.img bs=1M count=64
 ~ dd if=/usr/share/qemu-efi-aarch64/QEMU_EFI.fd of=flash0.img conv=notrunc
```
 * Create the root image, partition + format it (if you don't plan on installing GUI / ... 8G is more than enough):
```bash
 ~ qemu-img create arch.img 8G
 ~ sudo fdisk arch.img
```
 Now this part is the same as in Will's post:
 - g (to create a new GPT partition table)
 - n (to create a new partition), then enter twice, then +200M and enter
 - t (to change the type), then 1 for EFI System Partition
 - n and enter three times
 - w to write changes and exit
```
  ~ sudo kpartx arch.img
```
This will tell you the mapper devices for the image, mkfs the 200M one with vfat, the other one with ext4.
 * Copy the base system
```
 ~ mkdir root
 ~ sudo mount <fs with ext4> root
 ~ mkdir root/boot
 ~ sudo mount <fs with vfat> root/boot
 ~ bsdtar -xpf ArchLinuxARM-aarch64-latest.tar.gz -C root (x = extract, p = permissions, f = file)
```
 * Setup the base system:
```
 ~ blkid
```
will show you the UUID for the two mapped fs, enter them into root/etc/fstab:
```
UUID=XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX / ext4 defaults 0 0
UUID=XXXX-XXXX /boot vfat defaults 0 0
```
Edit root/boot/startup.nsh to contain only this line:
```
Image root=UUID=XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX rw initrd=\initramfs-linux.img loglevel=4
```
You can freely add/remove kernel parameters here.

 * Unmount everything, (optionally) convert to qcow2:
 ```
  sudo umount -r root
	sudo kpartx -d arch.img
	sync
	qemu-img convert -O qcow2 arch.img arch.qcow2
 ```
 * Create a `launch.sh` with this contents:
```
qemu-system-aarch64 \
	-nographic -machine virt,gic-version=max -m 8G -cpu max -smp 4 \
	-netdev user,id=vnet,hostfwd=:127.0.0.1:0-:22 \
	-device virtio-net-pci,netdev=vnet \
	-drive file=arch.qcow2,format=qcow2,if=none,id=drive0,cache=writeback \
	-device virtio-blk,drive=drive0,bootindex=0 \
	-drive file=flash0.img,format=raw,if=pflash \
	-drive file=flash1.img,format=raw,if=pflash 
```
And run it.

There's a lot of space for optimizations, as
 - the system's performance is very poor
 - lot of debug info spammeed at startup
 
More info:
 - Arch wiki
 - Arch Arm Forum
 - ...

sudo kpartx -av arch.img