1. A system comprising: a plurality of physical resources; a virtual overlay infrastructure comprising virtual machines mapped onto the plurality of physical resources; and a controller to passivate the virtual overlay infrastructure by suspending operations of all of the virtual machines in the virtual overlay infrastructure, during the passivation of the virtual overlay infrastructure, determine whether physical resource reservations for the virtual machines are to be changed, and reactivate the operations of all of the virtual machines in the virtual overlay infrastructure subsequent to the passivation of the virtual overlay infrastructure.