I'm playing with firmware='efi', with pending fedora edk2 packages, inprogress here: https://koji.fedoraproject.org/koji/buildinfo?buildID=1312544

virt-install from git with this command line: ./virt-install --os-variant fedora29 --disk none --transient --destroy-on-exit --boot firmware=efi --arch aarch64 --debug --rng none --channel none --network none

Generates this XML:
<domain type="qemu">
  <name>fedora29-aarch64</name>
  <uuid>c6be35c1-6ba3-46d8-98fb-c8984be2d3da</uuid>
  <metadata>
    <libosinfo:libosinfo xmlns:libosinfo="http://libosinfo.org/xmlns/libvirt/domain/1.0">
      <libosinfo:os id="http://fedoraproject.org/fedora/29"/>
    </libosinfo:libosinfo>
  </metadata>
  <memory>2097152</memory>
  <currentMemory>2097152</currentMemory>
  <vcpu>2</vcpu>
  <os firmware="efi">
    <type arch="aarch64" machine="virt">hvm</type>
    <loader readonly="yes" type="pflash">/usr/share/AAVMF/AAVMF_CODE.fd</loader>
    <boot dev="hd"/>
  </os>
  <features>
    <acpi/>
  </features>
  <cpu mode="custom" match="exact">
    <model>cortex-a57</model>
  </cpu>
  <clock offset="utc"/>
  <devices>
    <emulator>/usr/bin/qemu-system-aarch64</emulator>
    <controller type="usb" index="0" model="qemu-xhci" ports="15"/>
    <console type="pty"/>
    <memballoon model="virtio"/>
  </devices>
</domain>

Which raises this libvirt error: unsupported configuration: ACPI requires UEFI on this architecture

Which comes from this check in qemu_domain.c

    /* On aarch64, ACPI requires UEFI */                                         
    if (def->features[VIR_DOMAIN_FEATURE_ACPI] == VIR_TRISTATE_SWITCH_ON &&      
        def->os.arch == VIR_ARCH_AARCH64 &&                                      
        (!def->os.loader ||                                                      
         def->os.loader->type != VIR_DOMAIN_LOADER_TYPE_PFLASH)) {               
        virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",                         
                       _("ACPI requires UEFI on this architecture"));            
        goto cleanup;                                                            
    }  


So virt-install is setting acpi=True, but not setting loader=pflash, and this fails. But it's weird for a few reasons

* qemu_command.c doesn't even have any way to turn off acpi for aarch64, so whether acpi is specified or not doesn't have any command line effect AFAICT.
* If I set --features acpi=off, the VM starts fine, and type='pflash' seems to get filled in by default anyways
* If I change the XML to have this:

  <os firmware="efi">
    <type arch="aarch64" machine="virt">hvm</type>
    <loader type="pflash"/>
    <boot dev="hd"/>
  </os>

libvirt _still_ throws the same above error. I didn't dig into it more than that though. Basically via the XML I can't seem to get aarch64 firmware=efi to work with <acpi/> specified