There's more cool stuff coming in this area too. For a long time there's been the virtio family of protocols for shuttling IO to something outside QEMU to handl

There's more cool stuff coming in this area too. For a long time there's been the virtio family of protocols for shuttling IO to something outside QEMU to handle. Originally that was always KVM and the implementation is called vhost. Then later it became clear that these same messages could be sent to another user space process to handle instead (called vhost-user). These work great for creating virtio devices in the guest. But operating systems like Windows don't have virtio device drivers in-box, so it's a little annoying. Recently, a new protocol to replace virtio has been defined. It is modeled on vfio ioctls and currently only can forward to another user space process, so we're calling it vfio-user. With this protocol, it's possible to emulate any PCI device rather than only virtio devices. Projects like SPDK (what I work on) can now use this to present fully emulated NVMe devices into guests and back them with whatever actual storage is available (a file, something over the network, a real NVMe SSD, etc). This allows an OS, including Windows, to boot from the virtual disk using it's in-box NVMe driver. This hasn't quite made it into a QEMU release yet, but it's close!