#! /usr/bin/env bash

# Test a virtual machine with KVM on Apple M1. Notes:
#
# - Need QEMU 7 or later.
# - Login via VNC to :5901.
# - Expect to find QEMU_EFI.fd and QEMU_VARS.fd next to disk.img.
# - Installing with -cdrom does not work, have to use scsi-cd:
#
#   -device virtio-scsi-pci,id=scsi0 \
#   -drive if=none,id=cd,file=/tmp/debian-....iso \
#   -device scsi-cd,drive=cd
#
# - Replaced -usb (EHCI) with -device qemu-xhci (XHCI).
# - Added virtio-gpu-pci (otherwise no graphical output).
# - Added usb-kbd (otherwise no keyboard).
# - Note: position of netdev dictates enp0sN name, so keep first PCI device.
# - Must run on either P or E cores (https://gitlab.com/qemu-project/qemu/-/issues/1002).
# - On M1 0-3 are E, 4-7 are P (lscpu, lscpu -e).
# - On M1 Max 0-1 are E, 2-9 are P.
#
# -n <nic>
#   Network adapter to use, for example, virtio-net-pci (default), e1000,
#   or vmxnet3.
#
# -t <tap>
#   Existing tap interface to use instead of creating a new one (as tap9).
#
usage="usage: $0 [-n <nic>] <machine-dir> [<qemu-option>...]"

owd="$(pwd)"
trap "{ cd '$owd'; exit 1; }" ERR
set -o errtrace # Trap in functions.

function info () { echo "$*" 1>&2; }
function error () { info "$*"; exit 1; }

br=br0
mac="de:ad:be:ef:b8:da"

arch="$(uname -m)"
kvm=(taskset -c 4-7 "qemu-system-$arch" -enable-kvm)

nic=virtio-net-pci
etap=

while [ "$#" -gt 0 ]; do
  case "$1" in
    -n)
      shift
      nic="$1"
      shift
      ;;
    -t)
      shift
      etap="$1"
      shift
      ;;
    *)
      break
      ;;
  esac
done


dir="${1%/}"
shift

if [ -z "$dir" ]; then
  error "missing machine directory"
fi

if [ -z "$etap" ]; then
  tap=tap9
  sudo ip tuntap delete "$tap" mode tap || true
  sudo ip tuntap add "$tap" mode tap user "$(whoami)"
  sudo ip link set "$tap" up
  #sleep 0.5s
  sudo ip link set "$tap" master "$br"
else
  tap="$etap"
fi

"${kvm[@]}" \
  -machine virt \
  \
  -m 4G \
  -cpu host -smp "4,sockets=1,cores=4,threads=1" \
  \
  -drive "if=pflash,format=raw,readonly=on,file=$dir/QEMU_EFI.fd" \
  -drive "if=pflash,format=raw,file=$dir/QEMU_VARS.fd" \
  \
  -netdev "tap,id=net0,ifname=$tap,script=no" \
  -device "$nic,netdev=net0,mac=$mac" \
  \
  -drive  "if=none,id=disk0,file=$dir/disk.img,format=raw" \
  -device "virtio-blk-pci,scsi=off,drive=disk0" \
  \
  -device qemu-xhci \
  -device usb-kbd \
  -device usb-tablet \
  \
  -device virtio-gpu-pci \
  -display default,show-cursor=on \
  \
  -vnc :1 \
  \
  -chardev stdio,id=qmp \
  -mon chardev=qmp,mode=control,pretty=on \
  \
  -boot c "$@"

if [ -z "$etap" ]; then
  sudo ip tuntap delete "$tap" mode tap
fi