Paravirtualized cluster mode for legacy apics

A method comprising:

• with a guest using a legacy Advanced Programmable Interrupt Controller (APIC), determining that a hypervisor supports a paravirtualized cluster mode, the paravirtualized cluster mode allowing for interrupts using logical destination mode on a virtual machine having a plurality of virtual cores that is greater than eight;
• with the guest, enabling the paravirtualized cluster mode;
• associating each of the plurality of virtual cores with an N-bit identifier formatted to be one of 2N different values;
• and
• with the guest, setting N bits in a logical destination register to indicate the N-bit identifier associated with a virtual core of the plurality of virtual cores.

A computing system comprising:

• a processor;
• and
• a memory comprising machine readable instructions that when executed by the processor, cause the system to:
• advertise a paravirtualized cluster mode for a guest using a legacy Advanced Programmable Interrupt Controller (APIC), the paravirtualized cluster mode allowing for interrupts using logical destination mode on a virtual machine having a plurality of virtual cores that is greater than eight;
• associate each of the plurality of virtual cores with an N-bit identifier formatted to be one of 2N different values;
• and
• in response to receiving an interrupt for the virtual machine, determine to which of the plurality of virtual cores the interrupt should be sent based on at least a subset of bits in a destination address of the interrupt.