In a computing system having a processor package, an operating system, and a physical I/O device, a partial virtual machine is provided to instantiate a virtual I/O device corresponding to the physical I/O device, the virtual I/O device having a virtual I/O controller. The partial virtual machine includes an I/O port trap to capture an I/O request to the virtual I/O device by the operating system; an I/O controller emulator coupled to the I/O port trap to handle an I/O control request to the virtual I/O controller, when the I/O request comprises an I/O control request; an I/O device emulator coupled to the I/O port trap component to handle an I/O access request to communicate with the virtual I/O device, when the I/O request comprises an I/O access request; and a device driver coupled to the I/O controller emulator and the I/O device emulator to communicate with the physical I/O device based at least in part on the I/O control request and the I/O access request. The partial virtual machine executes within a secure enclave session within the processor package, improving security of I/O transactions by preventing access to the partial virtual machine by the operating system.