Multi-hypervisor virtual machines

A method of operating a computer system, comprising:

• providing a virtual machine and at least two independent hypervisors;
• executing the virtual machine under concurrent control of the at least two independent hypervisors;
• and
• maintaining a memory map comprising at least one logical memory page;
• translating through each of the at least two independent hypervisors an address of the at least one logical memory page having a common host physical address.

A computing system comprising:

• a unitary host machine;
• a privileged hypervisor, executing on the unitary host machine;
• a plurality of nested hypervisors, concurrently executing on the privileged hypervisor;
• and
• a plurality of virtual machines, each configured to issue input/output request for servicing by a respective nested hypervisor, at least one of the plurality of virtual machines concurrently executing under at least two of the plurality of nested hypervisors,
• wherein at least one of:
• input/output requests of the at least one virtual machine executing a task is serviced by a plurality of virtual machines;
• the virtual machine is configured to perform a first action which employs resources provided by a first nested hypervisor, and to perform a second action which employs resources provided by a second nested hypervisor, at least one input/output request of the virtual machine being services by the first nested hypervisor, substantially without interference by the second nested hypervisor;
• and
• a third nested hypervisor relays input/output requests or device interrupts from the virtual machine to a fourth nested hypervisor for processing by the fourth nested hypervisor.