Methods and systems for instantiating a virtual function in a partition of a multi-partition virtualization system implemented at least in part on a computing device are disclosed. One method includes initializing a partition on the computing device, including determining a virtual function to be associated with the partition, the virtual function associated with a physical function of an I/O device, and, prior to attaching a processor to the partition, determining if the physical function is in a ready state and capable of being associated with the virtual function. The method further includes, upon determining that the physical function is in the ready state and capable of being associated with the virtual function, attaching the processor to the partition, thereby allowing the partition to begin execution.