nixConfig/nixos/roles/xen_guest.nix

{...}: {
  imports = [ ];
  boot = {
    loader.grub = {
      device = "nodev";
      enable = true;
    };
    initrd = {
      availableKernelModules = [ "ata_piix" "sr_mod" "xen_blkfront" ];
      kernelModules = [ ];
    };
    extraModulePackages = [ ];
    tmp.useTmpfs = true;
  };
}