Re: https://firmwaresecurity.com/2018/11/27/amazon-com-announces-firecracker-a-secure-open-source-microvm/ and https://firmwaresecurity.com/2018/06/12/nemu-fork-of-qemu-by-intel/
Microvm is a machine type inspired by both NEMU and Firecracker, and constructed after the machine model implemented by the latter. It’s main purpose is providing users a KVM-only machine type with fast boot times, minimal attack surface (measured as the number of IO ports and MMIO regions exposed to the Guest) and small footprint (specially when combined with the ongoing QEMU modularization effort). Normally, other than the device support provided by KVM itself, microvm only supports virtio-mmio devices. Microvm also includes a legacy mode, which adds an ISA bus with a 16550A serial port, useful for being able to see the early boot kernel messages.[…]
https://lists.gnu.org/archive/html/qemu-devel/2019-06/msg06211.html
Firmware Security 