Nova supports configuring a UEFI
bootloader for guests. This brings about important advantages over
legacy BIOS bootloaders and allows for features such as secure-boot.

Enabling UEFI

Currently the configuration of UEFI guest bootloaders is only
supported when using the libvirt compute driver with a libvirt.virt_type of kvm
or qemu or when using the Hyper-V compute driver with
certain machine types. When using the libvirt compute driver with
AArch64-based guests, UEFI is automatically enabled as AArch64 does not
support BIOS.

Configuring a flavor or
image

Configuring a UEFI bootloader varies depending on the compute driver
in use.

Libvirt

UEFI support is enabled by default on AArch64-based guests. For other
guest architectures, you can request UEFI support with libvirt by
setting the hw_firmware_type image property to
uefi. For example:

$ openstack image set --property hw_firmware_type=uefi $IMAGE

Hyper-V

It is not possible to explicitly request UEFI support with Hyper-V.
Rather, it is enabled implicitly when using Generation
2 guests. You can request a Generation 2 guest by setting the
hw_machine_type image metadata property to
hyperv-gen2. For example:

$ openstack image set --property hw_machine_type=hyperv-gen2 $IMAGE

References

• Hyper-V
  UEFI Secure Boot (spec)
• Open
  Virtual Machine Firmware (OVMF) Status Report
• Anatomy
  of a boot, a QEMU perspective
• Should
  I create a generation 1 or 2 virtual machine in Hyper-V?