In a computer system, joint operation of multiple hypervisors is coordinated. A persistent hypervisor and a non-persistent hypervisor are executed. The non-persistent hypervisor is executed in the supervisor mode according to an operating regime controlled by a scheduler engine, and the persistent hypervisor is executed in the hypervisor mode under the control of a handler engine. The handler engine monitors, and responds, to an attempted mode transition of the processor between the hypervisor and supervisor modes, and coordinates the suspension and resumption, as appropriate, of the persistent hypervisor.