Unfortunately VENOM was not so easy because some OSes (ehm Windows XP but also 2003...) only support driver floppies as opposed to driver CD-ROMs.
But we disable a bunch of old SCSI adapters, NICs, most audio cards, the whole Bluetooth emulation subsystem. All the cross-architecture emulation is also compiled out (x86-on-x86 emulation is still left in, until nested virtualization matures---which the Google folks are helping us with too!---but we only support it for libguestfs appliances).
Furthermore, in RHEL most image formats are forbidden or only supported read-only in the emulator (you can still use qemu-img to convert to and from them). Read-only support can be useful because of virt-v2v, an appliance that reads from VMware or Hyper-V images and tweaks them to run as KVM guests.
But we disable a bunch of old SCSI adapters, NICs, most audio cards, the whole Bluetooth emulation subsystem. All the cross-architecture emulation is also compiled out (x86-on-x86 emulation is still left in, until nested virtualization matures---which the Google folks are helping us with too!---but we only support it for libguestfs appliances).
Furthermore, in RHEL most image formats are forbidden or only supported read-only in the emulator (you can still use qemu-img to convert to and from them). Read-only support can be useful because of virt-v2v, an appliance that reads from VMware or Hyper-V images and tweaks them to run as KVM guests.