1. A computer-readable storage medium for using a running operating system to launch a hypervisor, bearing computer-readable instructions that, upon execution by a computer, cause operations comprising: launching, by the operating system, the hypervisor; discovering, by the operating system, a physical resource of the computer; providing, by the operating system, state information for the physical resource to the hypervisor, the state information including at least an identification of the physical resource; pausing the operating system; launching, by the hypervisor, a virtual machine instance for the operating system; initializing the virtual machine instance with state consistent with the state information; resuming, by the hypervisor, the operating system after initializing the virtual machine instance; and after the operating system is resumed, using, by the hypervisor, the virtual machine instance to virtualize the physical resource to the operating system.