libvirt now supports OVMF

Thanks to the work of Michal Privoznik and support of Laszlo Ersek and others, libvirt can now manage VMs using OVMF natively.  If you're on Fedora and using Gerd's OVMF RPMs, you simply need to create a copy of /usr/share/edk2.git/ovmf-x64/OVMF-pure-efi.fd for each VM (put it somewhere like /var/lib/libvirt/images/), and make it writable (support is still new and it doesn't seem to change file permissions for the VM yet).  Then, edit the domain XML to include this:

<domain type='kvm'>
  ...
  <os>
    ...
    <loader type='pflash'>/var/lib/libvirt/images/VM1-OVMF.fd</loader>
  </os>
</domain>

Since the OVMF image we're using is a "unified" image, it contains both the UEFI code itself as well as variable storage space, so the above adds it as writable by the VM.  There are also ways to have a split image so you can maintain the UEFI code separate from the variables, but I'll wait for builds from Gerd that support that before I attempt to document it.

With support for both the kvm=off cpu option and OVMF in libvirt, we're now able to run completely native libvirt VMs with GeForce and Radeon GPU assignment.  Support is already underway for virt-manager and virt-install of OVMF.

Also, a VM CPU selection tip, since we don't care about migration with an assigned GPU, there are few reasons left not to want to use the -cpu host option for QEMU.  To enable that through libvirt, change the CPU definition in the XML to this:

<domain type='kvm'>
  ...
  <cpu mode='host-passthrough'/>
  ...
</domain>

Automatic vCPU pinning is also available:

<domain type='kvm'>
  ...
  <cputune>
    <vcpupin vcpu='0' cpuset='0'/>
    <vcpupin vcpu='1' cpuset='1'/>
  </cputune>
  ...
</domain>

And yes, hugepage support is also available, see libvirt documentation for details.  Enjoy.