# Xen 安装与配置

Xen 分为 Xen Hypervisor、Dom 0 和 Dom U。针对 Xen Hypervisor 需要提供引导配置，针对 Dom U 需要提供虚拟机配置。

## 安装

在 ArchLinux/Manjaro 上通过 yaourt 进行安装。

```bash
yaourt -S xen
```

提示需要 83FE14C957E82BD9 密钥：

```bash
# 注意不要加 sudo，因为 root 和每个普通账户的密钥是分别存储的
gpg --recv-keys 83FE14C957E82BD9
gpg --lsign-key 83FE14C957E82BD9
gpg --finger 83FE14C957E82BD9
```

还需要装一些额外的软件包：

```bash
sudo pacman -S seabios ovmf mesa bluez-libs
```

## Grub 引导配置

### Grub 参考引导配置文件

在 ArchLinux/Manjaro 上安装完 Xen 后，在 /etc/grub.d/09_xen 为 Xen Hypervisor 的参考引导配置文件（基于 Grub），内容如下：

```ini
#!/usr/bin/env bash

##
## grub-mkconfig helper script specific to Arch Linux
## Contributed by "Keshav Amburay" <the ddoott ridikulus ddoott rat aatt geemmayil ddoott ccoomm>
## Updated on 08 February 2014
##
## Script based on do_grub_config() function in Arch Linux Archboot ISO Installer/Setup script
## Some parts taken from /etc/grub.d/10_linux script shipped by GRUB(2) upstream
##
## This script can be freely distributed and/or modified
## under the terms of the GNU General Public License as published by
## the Free Software Foundation, either version 3 of the License, or
## (at your option) any later version.
##
## This script is distributed in the hope that it will be useful,
## but WITHOUT ANY WARRANTY; without even the implied warranty of
## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
## GNU General Public License for more details.
##

## Adapted for use with the xen AUR package, to ensure feature comparity
## Modified by "David Sutton" <kantras - gmail com>

_FUNC_GRUB_FILE_PRESENT() {

    [[ -z "${GRUB_PLATFORM}" ]] && GRUB_PLATFORM="x86"

    if [[ "${GRUB_PLATFORM}" == "x86" ]]; then
        check="--is-x86-linux32"
    elif [[ "${GRUB_PLATFORM}" == "i386-xen-pae" ]]; then
        check="--is-i386-xen-pae-domu"
    elif [[ "${GRUB_PLATFORM}" == "x86_64-xen" ]]; then
        check="--is-x86_64-xen-domu"
    else
        check="--is-${GRUB_PLATFORM}-linux"
    fi

    case "${GRUB_PLATFORM}" in
        x86)
            list="$(for i in "${GRUB_ROOT}"/boot/vmlinuz-linux* ; do
                        if grub_file_is_not_garbage "${i}" && "${grub_file}" ${check} "${i}" ; then echo -n "${i} " ; fi
                    done)" ;;
        *)
          list="$(for i in "${GRUB_ROOT}"/boot/vmlinuz-linux* ; do
                      if grub_file_is_not_garbage "${i}" && "${grub_file}" ${check} "${i}" ; then echo -n "${i} " ; fi
                  done)" ;;
    esac
}

set -e

prefix="/usr"
exec_prefix="${prefix}"
datarootdir="/usr/share"
datadir="${datarootdir}"
sysconfdir="/etc"

. "${datarootdir}/grub/grub-mkconfig_lib"

. "${sysconfdir}/default/grub"

export XEN_HYPERVISOR_CMDLINE="xsave=1"
export XEN_LINUX_CMDLINE="console=tty0"

[[ -r "${sysconfdir}/xen/grub.conf" ]] && . "${sysconfdir}/xen/grub.conf"

[[ -z "${XEN_LINUX_CMDLINE_OVERRIDE}" ]] && XEN_LINUX_CMDLINE_OVERRIDE="0"

export TEXTDOMAIN="grub"
export TEXTDOMAINDIR="${datarootdir}/locale"

CLASS="--class xen --class arch-linux --class arch --class gnu-linux --class gnu --class os"

[[ "${grub_file}" != "" ]] && _FUNC_GRUB_FILE_PRESENT

BOOT_PART_FS_UUID="$(${grub_probe} --target="fs_uuid" "/boot" 2>/dev/null)"
BOOT_PART_HINTS_STRING="$(${grub_probe} --target="hints_string" "/boot" 2>/dev/null || true)"
BOOT_PART_FS="$(${grub_probe} --target="fs" "/boot" 2>/dev/null)"

ROOT_PART_GRUB_DEVICE="$(${grub_probe} --target=device / || true)"
ROOT_PART_FS="$(${grub_probe} --device ${ROOT_PART_GRUB_DEVICE} --target=fs 2> /dev/null || echo "unknown")"

if [[ "${GRUB_LINUX_ROOT_DEVICE}" == "" ]]; then

    case "${ROOT_PART_FS}" in
        btrfs)
            rootsubvol="$(make_system_path_relative_to_its_root /)"
            rootsubvol="${rootsubvol#/}"
            if [[ "${rootsubvol}" != "" ]]; then
                GRUB_LINUX_ROOT_DEVICE="subvol=${rootsubvol}"
            fi
        ;;
        zfs)
            rpool="$(${grub_probe} --device ${GRUB_DEVICE} --target=fs_label 2>/dev/null || true)"
            bootfs="$(make_system_path_relative_to_its_root / | sed -e "s,@$,,")"
            GRUB_LINUX_ROOT_DEVICE="ZFS=${rpool}${bootfs}"
        ;;
    esac

    if [[ "${GRUB_DEVICE_UUID}" == "" ]] || \
       [[ "${GRUB_DISABLE_LINUX_UUID}" == "true" ]] || \
       [[ ! -e "/dev/disk/by-uuid/${GRUB_DEVICE_UUID}" ]] || \
       uses_abstraction "${GRUB_DEVICE}" lvm ; then
           GRUB_LINUX_ROOT_DEVICE="${GRUB_DEVICE}"
    else
       GRUB_LINUX_ROOT_DEVICE="UUID=${GRUB_DEVICE_UUID}"
    fi
fi

[[ "${GRUB_LINUX_PARAMS}" == "" ]] && GRUB_LINUX_PARAMS="${GRUB_CMDLINE_LINUX} ${GRUB_CMDLINE_LINUX_DEFAULT}"
if [[ "${XEN_LINUX_CMDLINE_OVERRIDE}" == "0" ]]; then
    GRUB_LINUX_PARAMS="${GRUB_LINUX_PARAMS} ${XEN_LINUX_CMDLINE}"
else
    GRUB_LINUX_PARAMS="${XEN_LINUX_CMDLINE}"
fi

xen_list=`for i in /boot/xen-*.gz /xen-*.gz ; do
       if grub_file_is_not_garbage "$i" ; then echo -n "$i "; fi
done`

while [ "x$xen_list" != "x" ] ; do
    xen=`version_find_latest $xen_list`
    echo "Found Xen hypervisor image: $xen" >&2
    XEN_BASENAME=`basename $xen`
    XEN_VERSION=`echo $XEN_BASENAME | sed -e "s,^[^0-9]*-,,g" | sed -e "s,.gz,,g"`

    for _KERNEL_ in ${list} ; do

        echo "Found linux image: ${_KERNEL_}" >&2

        basename="$(basename "${_KERNEL_}")"
        dirname="$(dirname "${_KERNEL_}")"
        REAL_DIR="$(make_system_path_relative_to_its_root "${dirname}")"

        _KERNEL_FILE_="$(echo ${_KERNEL_} | sed 's,/boot/,,g')"
        _KERNEL_PKG_="pkg-$(echo ${_KERNEL_FILE_} | sed 's,vmlinuz-,,g')"

        _INITRAMFS_="${_KERNEL_FILE_/vmlinuz-/initramfs-}.img"

        if [[ -e "/boot/${_INITRAMFS_}" ]]; then

            echo "Found initramfs image: /boot/${_INITRAMFS_}" >&2

            cat << EOF

menuentry "Xen ${XEN_VERSION} / Arch Linux ${_KERNEL_PKG_} kernel" ${CLASS} {
    $(save_default_entry)
    if [ x\$feature_all_video_module = xy ]; then
        insmod all_video
    fi
    set gfxpayload=keep
    insmod ${BOOT_PART_FS}
    if [ x\$feature_platform_search_hint = xy ]; then
        search --no-floppy --fs-uuid  --set=root ${BOOT_PART_HINTS_STRING} ${BOOT_PART_FS_UUID}
    else
        search --no-floppy --fs-uuid  --set=root ${BOOT_PART_FS_UUID}
    fi
    echo '$(printf "Loading Xen %s ..." ${XEN_VERSION})'
    multiboot2 ${REAL_DIR}/${XEN_BASENAME} ${XEN_HYPERVISOR_CMDLINE}
    echo 'Loading Arch Linux ${_KERNEL_PKG_} kernel ...'
    module2 ${REAL_DIR}/${_KERNEL_FILE_} root=${GRUB_LINUX_ROOT_DEVICE} rw ${GRUB_LINUX_PARAMS}
    echo 'Loading Arch Linux ${_KERNEL_PKG_} kernel initramfs ...'
    module2 ${REAL_DIR}/${_INITRAMFS_}
}

EOF
        fi

        _INITRAMFS_FALLBACK_="${_KERNEL_FILE_/vmlinuz-/initramfs-}-fallback.img"

        if [[ -e "/boot/${_INITRAMFS_FALLBACK_}" ]]; then

            echo "Found fallback initramfs image: /boot/${_INITRAMFS_FALLBACK_}" >&2

            cat << EOF

menuentry "Xen ${XEN_VERSION} / Arch Linux ${_KERNEL_PKG_} kernel (fallback initramfs)" ${CLASS} {
    $(save_default_entry)
    if [ x\$feature_all_video_module = xy ]; then
        insmod all_video
    fi
    set gfxpayload=keep
    insmod ${BOOT_PART_FS}
    if [ x\$feature_platform_search_hint = xy ]; then
        search --no-floppy --fs-uuid  --set=root ${BOOT_PART_HINTS_STRING} ${BOOT_PART_FS_UUID}
    else
        search --no-floppy --fs-uuid  --set=root ${BOOT_PART_FS_UUID}
    fi
    echo '$(printf "Loading Xen %s ..." ${XEN_VERSION})'
    multiboot2 ${REAL_DIR}/${XEN_BASENAME} ${XEN_HYPERVISOR_CMDLINE}
    echo 'Loading Arch Linux ${_KERNEL_PKG_} kernel ...'
    module2 ${REAL_DIR}/${_KERNEL_FILE_} root=${GRUB_LINUX_ROOT_DEVICE} rw ${GRUB_LINUX_PARAMS}
    echo 'Loading Arch Linux ${_KERNEL_PKG_} kernel fallback initramfs ...'
    module2 ${REAL_DIR}/${_INITRAMFS_FALLBACK_}
}

EOF
        fi

        if [[ ! -e "/boot/${_INITRAMFS_}" ]] && [[ ! -e "/boot/${_INITRAMFS_FALLBACK_}" ]]; then
            cat << EOF

menuentry "Xen ${XEN_VERSION} / Arch Linux ${_KERNEL_PKG_} kernel (no initramfs)" ${CLASS} {
    $(save_default_entry)
    if [ x\$feature_all_video_module = xy ]; then
        insmod all_video
    fi
    set gfxpayload=keep
    insmod ${BOOT_PART_FS}
    if [ x\$feature_platform_search_hint = xy ]; then
        search --no-floppy --fs-uuid  --set=root ${BOOT_PART_HINTS_STRING} ${BOOT_PART_FS_UUID}
    else
        search --no-floppy --fs-uuid  --set=root ${BOOT_PART_FS_UUID}
    fi
    echo '$(printf "Loading Xen %s ..." ${XEN_VERSION})'
    multiboot2 ${REAL_DIR}/${XEN_BASENAME} ${XEN_HYPERVISOR_CMDLINE}
    echo 'Loading Arch Linux ${_KERNEL_PKG_} kernel ...'
    module2 ${REAL_DIR}/${_KERNEL_FILE_} root=${GRUB_LINUX_ROOT_DEVICE} rw ${GRUB_LINUX_PARAMS}
}

EOF
        fi

    done

    xen_list=`echo $xen_list | tr ' ' '\n' | grep -vx $xen | tr '\n' ' '`
done
```

### 一个简化的 Grub 配置参考

一个简化的 Grup 引导配置文件如下，其中 xen-4.12.1.gz 为 Xen Hypervisor，vmlinuz-4.9-x86_64 为支持 Xen 的 Dom 0 Linux Kernel，initramfs-4.9-x86_64.img 为 RAM Disk。注意当前的根为“/boot”而非“/”。"xsave=1" "dom0_max_vcpus=1" "dom0_mem=1024M" 为 Xen Hypervisor，vmlinuz 的 Command Line Options。root=UUID=xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx rw  quiet udev.log_priority=3 为 Dom 0 Kernel Command Line Options。

```ini
menuentry "Xen / Arch Linux kernel" --class manjaro --class gnu-linux --class gnu --class os {
    savedefault
    load_video
    set gfxpayload=keep
    insmod gzio
    insmod part_msdos
    insmod ext2
    set root='hd0,msdos1'
    if [ x$feature_platform_search_hint = xy ]; then
        search --no-floppy --fs-uuid --set=root --hint-bios=hd0,msdos1 --hint-efi=hd0,msdos1 --hint-baremetal=ahci0,msdos1  xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx
    else
        search --no-floppy --fs-uuid --set=root xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx
    fi
    multiboot2 /xen-4.12.1.gz "xsave=1" "dom0_max_vcpus=1" "dom0_mem=1024M"
    echo  'Loading kernel ...'
    module2 /vmlinuz-4.9-x86_64 root=UUID=xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx rw  quiet udev.log_priority=3
    echo  'Loading initial ramdisk ...'
    module2 /initramfs-4.9-x86_64.img
}
```

## Systemd-boot 引导配置

Systemd-boot 无法直接引导 xen-4.12.1.gz，并且配置其参数。但是 Systemd-boot 可以引导 efi 文件，因此可以先引导 xen-4.12.1.efi，再由 xen-4.12.1.efi 引导 Dom0 内核进行启动。xen-4.12.1.efi 需要一个配置文件用于配置 Dom0。但在此之前，先要编写 Systemd-boot 的 entry 文件 /boot/loader/entries/10-xen.conf 文件，用于引导 xen-4.12.1.efi：

```ini
title   Xen Hypervisor
efi     /xen-4.12.1.efi
```

之后在 /boot 目录下创建 xen-4.12.1.cfg 文件用于配置 Dom0：

```ini
[global]
default=xen

[xen]
options=loglvl=all noreboot=true reboot=no dom0_max_vcpus=3 dom0_mem=6000M
ucode=intel-ucode.img
kernel=vmlinuz-5.3-x86_64 root=PARTUUID=xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx rw
ramdisk=initramfs-5.3-x86_64.img
```

xen-4.12.1.efi 会按照一定规则查找 cfg 文件，首先会查找与自身同名但是扩展名为 cfg 的文件，最后会查找 xen.cfg 文件。更详细的规则可以参考官方帮助。

## DomU

DomU 的使用和配置请参考 [Xen DomU 配置与使用](Xen_DomU_配置与使用.md)

## 外部参考资料

1. <https://xenbits.xen.org/docs/unstable/misc/efi.html>
2. [Xen-Arch Wiki](https://wiki.archlinux.org/index.php/Xen)