In this presentation Knut Omang will talk about how he has been deploying a patched version of QEMU/KVM as part of a framework to enable writing an almost functionally complete device driver for a complex new network device before any hardware was available. Different levels of simulation/emulation has different benefits and challenges. Detailed low level simulation of hardware is accurate but painfully slow. High level simulation/emulation is fast enough to run real workloads, but with somewhat lower precision. QEMU/KVM with device hot plugging allows recompiling/relinking/restarting different device models while keeping the guest(s) running. Even after availablity of hardware, the QEMU anchored models are valuable tools, as some testing can be run on the models, saving expensive server hardware, and also simplifying monitoring of traffic between device and driver.