xbt::signal<void(VirtualMachine&)> VirtualMachine::on_creation;
xbt::signal<void(VirtualMachine const&)> VirtualMachine::on_start;
xbt::signal<void(VirtualMachine const&)> VirtualMachine::on_started;
xbt::signal<void(VirtualMachine&)> VirtualMachine::on_creation;
xbt::signal<void(VirtualMachine const&)> VirtualMachine::on_start;
xbt::signal<void(VirtualMachine const&)> VirtualMachine::on_started;