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# Xen hypervisor (Dom0) support.
{ config, lib, pkgs, ... }:
with lib;
let
cfg = config.virtualisation.xen;
xen = pkgs.xen;
xendConfig = pkgs.writeText "xend-config.sxp"
''
(loglevel DEBUG)
(network-script network-bridge)
(vif-script vif-bridge)
'';
in
{
###### interface
options = {
virtualisation.xen.enable =
mkOption {
default = false;
description =
''
Setting this option enables the Xen hypervisor, a
virtualisation technology that allows multiple virtual
machines, known as <emphasis>domains</emphasis>, to run
concurrently on the physical machine. NixOS runs as the
privileged <emphasis>Domain 0</emphasis>. This option
requires a reboot to take effect.
'';
};
virtualisation.xen.bootParams =
mkOption {
default = "";
description =
''
Parameters passed to the Xen hypervisor at boot time.
'';
};
virtualisation.xen.domain0MemorySize =
mkOption {
default = 0;
example = 512;
description =
''
Amount of memory (in MiB) allocated to Domain 0 on boot.
If set to 0, all memory is assigned to Domain 0.
'';
};
};
###### implementation
config = mkIf cfg.enable {
environment.systemPackages = [ xen ];
# Domain 0 requires a pvops-enabled kernel.
boot.kernelPackages = pkgs.linuxPackages_3_2_xen;
boot.kernelModules =
[ "xen_evtchn" "xen_gntdev" "xen_blkback" "xen_netback" "xen_pciback"
"blktap" "tun"
];
# The radeonfb kernel module causes the screen to go black as soon
# as it's loaded, so don't load it.
boot.blacklistedKernelModules = [ "radeonfb" ];
# Increase the number of loopback devices from the default (8),
# which is way too small because every VM virtual disk requires a
# loopback device.
boot.extraModprobeConfig =
''
options loop max_loop=64
'';
virtualisation.xen.bootParams =
[ "loglvl=all" "guest_loglvl=all" ] ++
optional (cfg.domain0MemorySize != 0) "dom0_mem=${toString cfg.domain0MemorySize}M";
system.extraSystemBuilderCmds =
''
ln -s ${xen}/boot/xen.gz $out/xen.gz
echo "${toString cfg.bootParams}" > $out/xen-params
'';
# Mount the /proc/xen pseudo-filesystem.
system.activationScripts.xen =
''
if [ -d /proc/xen ]; then
${pkgs.sysvtools}/bin/mountpoint -q /proc/xen || \
${pkgs.utillinux}/bin/mount -t xenfs none /proc/xen
fi
'';
jobs.xend =
{ description = "Xen Control Daemon";
startOn = "stopped udevtrigger";
path =
[ pkgs.bridge_utils pkgs.gawk pkgs.iproute pkgs.nettools
pkgs.utillinux pkgs.bash xen pkgs.pciutils pkgs.procps
];
environment.XENCONSOLED_TRACE = "hv";
preStart =
''
mkdir -p /var/log/xen/console -m 0700
${xen}/sbin/xend start
# Wait until Xend is running.
for ((i = 0; i < 60; i++)); do echo "waiting for xend..."; ${xen}/sbin/xend status && break; done
${xen}/sbin/xend status || exit 1
'';
postStop = "${xen}/sbin/xend stop";
};
jobs.xendomains =
{ description = "Automatically starts, saves and restores Xen domains on startup/shutdown";
startOn = "started xend";
stopOn = "starting shutdown and stopping xend";
restartIfChanged = false;
path = [ pkgs.xen ];
environment.XENDOM_CONFIG = "${xen}/etc/sysconfig/xendomains";
preStart =
''
mkdir -p /var/lock/subsys -m 755
${xen}/etc/init.d/xendomains start
'';
postStop = "${xen}/etc/init.d/xendomains stop";
};
# To prevent a race between dhcpcd and xend's bridge setup script
# (which renames eth* to peth* and recreates eth* as a virtual
# device), start dhcpcd after xend.
jobs.dhcpcd.startOn = mkOverride 50 "started xend";
environment.etc =
[ { source = xendConfig;
target = "xen/xend-config.sxp";
}
{ source = "${xen}/etc/xen/scripts";
target = "xen/scripts";
}
];
# Xen provides udev rules.
services.udev.packages = [ xen ];
services.udev.path = [ pkgs.bridge_utils pkgs.iproute ];
};
}
|