I'm using OVMF and the XML is:
<domain type="kvm">
<name>freebsd13.0</name>
<uuid>b28ab815-5983-4598-9800-7f0fe1948b57</uuid>
<metadata>
<libosinfo:libosinfo xmlns:libosinfo="http://libosinfo.org/xmlns/libvirt/domain/1.0">
<libosinfo:os id="http://freebsd.org/freebsd/13.0"/>
</libosinfo:libosinfo>
</metadata>
<memory>16777216</memory>
<currentMemory>16777216</currentMemory>
<vcpu current="8">8</vcpu>
<os>
<type arch="x86_64" machine="q35">hvm</type>
<loader readonly="yes" type="pflash">/usr/share/edk2-ovmf/x64/OVMF_CODE.fd</loader>
<boot dev="hd"/>
</os>
<features>
<acpi/>
<apic/>
<vmport state="off"/>
</features>
<cpu mode="host-passthrough">
<topology sockets="1" cores="8" threads="1"/>
</cpu>
<clock offset="utc">
<timer name="rtc" tickpolicy="catchup"/>
<timer name="pit" tickpolicy="delay"/>
<timer name="hpet" present="no"/>
</clock>
<pm>
<suspend-to-mem enabled="no"/>
<suspend-to-disk enabled="no"/>
</pm>
<devices>
<emulator>/usr/bin/qemu-system-x86_64</emulator>
<disk type="file" device="disk">
<driver name="qemu" type="qcow2"/>
<source file="/home/rei/Documents/virt/vms/freebsd13.0"/>
<target dev="vda" bus="virtio"/>
</disk>
<disk type="file" device="cdrom">
<driver name="qemu" type="raw"/>
<source file="/home/rei/Documents/virt/iso/FreeBSD-13.1-RELEASE-amd64-disc1.iso"/>
<target dev="sda" bus="sata"/>
<readonly/>
</disk>
<controller type="usb" model="ich9-ehci1"/>
<controller type="usb" model="ich9-uhci1">
<master startport="0"/>
</controller>
<controller type="usb" model="ich9-uhci2">
<master startport="2"/>
</controller>
<controller type="usb" model="ich9-uhci3">
<master startport="4"/>
</controller>
<interface type="network">
<source network="default"/>
<mac address="52:54:00:71:00:a9"/>
<model type="virtio"/>
</interface>
<console type="pty"/>
<channel type="spicevmc">
<target type="virtio" name="com.redhat.spice.0"/>
</channel>
<sound model="ich6"/>
<hostdev mode="subsystem" type="pci" managed="yes">
<source>
<address domain="0" bus="12" slot="0" function="0"/>
</source>
</hostdev>
<hostdev mode="subsystem" type="pci" managed="yes">
<source>
<address domain="0" bus="12" slot="0" function="1"/>
</source>
</hostdev>
<hostdev mode="subsystem" type="pci" managed="yes">
<source>
<address domain="0" bus="14" slot="0" function="3"/>
</source>
</hostdev>
<redirdev bus="usb" type="spicevmc"/>
<redirdev bus="usb" type="spicevmc"/>
</devices>
</domain>