Embodiments of apparatuses, methods, and systems for injecting transactions to support the virtualization of a physical device controller are disclosed. In one embodiment, an apparatus includes a processor, system memory, a physical device controller, and a virtualization agent. The physical device controller is to be shared by a plurality of virtual machines created by a virtual machine monitor installed on a processor. The virtualization agent is coupled to the system memory through a first interface and coupled to the physical device controller through a second interface, to represent the physical device controller as a plurality of virtual device controllers available to be allocated to the plurality of virtual machines, and to inject transactions onto the first interface and the second interface on behalf of the plurality of virtual device controllers.