This is how my xml looks. I have a ryzen 2700x just to let you know.
<?xml version='1.0' encoding='UTF-8'?>
<domain type='kvm' id='11' xmlns:qemu='http://libvirt.org/schemas/domain/qemu/1.0'>
<name>Big Sur Dev GPU</name>
<uuid>666</uuid>
<metadata>
<vmtemplate xmlns="unraid" name="Linux" icon="BigSurCritter.png" os="linux"/>
</metadata>
<memory unit='KiB'>8388608</memory>
<currentMemory unit='KiB'>8388608</currentMemory>
<memoryBacking>
<nosharepages/>
</memoryBacking>
<vcpu placement='static'>8</vcpu>
<cputune>
<vcpupin vcpu='0' cpuset='4'/>
<vcpupin vcpu='1' cpuset='12'/>
<vcpupin vcpu='2' cpuset='5'/>
<vcpupin vcpu='3' cpuset='13'/>
<vcpupin vcpu='4' cpuset='6'/>
<vcpupin vcpu='5' cpuset='14'/>
<vcpupin vcpu='6' cpuset='7'/>
<vcpupin vcpu='7' cpuset='15'/>
</cputune>
<resource>
<partition>/machine</partition>
</resource>
<os>
<type arch='x86_64' machine='pc-q35-5.0'>hvm</type>
<loader readonly='yes' type='pflash'>/usr/share/qemu/ovmf-x64/OVMF_CODE-pure-efi.fd</loader>
<nvram>/etc/libvirt/qemu/nvram/666_VARS-pure-efi.fd</nvram>
</os>
<features>
<acpi/>
<apic/>
</features>
<cpu mode='host-passthrough' check='none'/>
<clock offset='utc'>
<timer name='rtc' tickpolicy='catchup'/>
<timer name='pit' tickpolicy='delay'/>
<timer name='hpet' present='no'/>
</clock>
<on_poweroff>destroy</on_poweroff>
<on_reboot>restart</on_reboot>
<on_crash>restart</on_crash>
<devices>
<emulator>/usr/local/sbin/qemu</emulator>
<disk type='file' device='disk'>
<driver name='qemu' type='qcow2' cache='none'/>
<source file='/mnt/cache/domains/Big Sur/opencore.bigsurv0611.qcow2' index='2'/>
<backingStore/>
<target dev='hdc' bus='usb'/>
<boot order='1'/>
<alias name='usb-disk2'/>
<address type='usb' bus='0' port='1'/>
</disk>
<disk type='file' device='disk'>
<driver name='qemu' type='qcow2' cache='none' io='native' discard='unmap'/>
<source file='/mnt/disks/MKNSSDRE500GB_MK170901100386B42/Hackintosh/Sir.img' index='1'/>
<backingStore/>
<target dev='hdd' bus='sata'/>
<alias name='sata0-0-3'/>
<address type='drive' controller='0' bus='0' target='0' unit='3'/>
</disk>
<controller type='usb' index='0' model='ich9-ehci1'>
<alias name='usb'/>
<address type='pci' domain='0x0000' bus='0x00' slot='0x07' function='0x7'/>
</controller>
<controller type='usb' index='0' model='ich9-uhci1'>
<alias name='usb'/>
<master startport='0'/>
<address type='pci' domain='0x0000' bus='0x00' slot='0x07' function='0x0' multifunction='on'/>
</controller>
<controller type='usb' index='0' model='ich9-uhci2'>
<alias name='usb'/>
<master startport='2'/>
<address type='pci' domain='0x0000' bus='0x00' slot='0x07' function='0x1'/>
</controller>
<controller type='usb' index='0' model='ich9-uhci3'>
<alias name='usb'/>
<master startport='4'/>
<address type='pci' domain='0x0000' bus='0x00' slot='0x07' function='0x2'/>
</controller>
<controller type='sata' index='0'>
<alias name='ide'/>
<address type='pci' domain='0x0000' bus='0x00' slot='0x1f' function='0x2'/>
</controller>
<controller type='pci' index='0' model='pcie-root'>
<alias name='pcie.0'/>
</controller>
<controller type='pci' index='1' model='pcie-root-port'>
<model name='pcie-root-port'/>
<target chassis='1' port='0x8'/>
<alias name='pci.1'/>
<address type='pci' domain='0x0000' bus='0x00' slot='0x01' function='0x0' multifunction='on'/>
</controller>
<controller type='pci' index='2' model='pcie-to-pci-bridge'>
<model name='pcie-pci-bridge'/>
<alias name='pci.2'/>
<address type='pci' domain='0x0000' bus='0x01' slot='0x00' function='0x0'/>
</controller>
<controller type='pci' index='3' model='pcie-root-port'>
<model name='pcie-root-port'/>
<target chassis='3' port='0x9'/>
<alias name='pci.3'/>
<address type='pci' domain='0x0000' bus='0x00' slot='0x01' function='0x1'/>
</controller>
<controller type='pci' index='4' model='pcie-root-port'>
<model name='pcie-root-port'/>
<target chassis='4' port='0xa'/>
<alias name='pci.4'/>
<address type='pci' domain='0x0000' bus='0x00' slot='0x01' function='0x2'/>
</controller>
<controller type='pci' index='5' model='pcie-root-port'>
<model name='pcie-root-port'/>
<target chassis='5' port='0xb'/>
<alias name='pci.5'/>
<address type='pci' domain='0x0000' bus='0x00' slot='0x01' function='0x3'/>
</controller>
<controller type='pci' index='6' model='pcie-root-port'>
<model name='pcie-root-port'/>
<target chassis='6' port='0xc'/>
<alias name='pci.6'/>
<address type='pci' domain='0x0000' bus='0x00' slot='0x01' function='0x4'/>
</controller>
<controller type='pci' index='7' model='pcie-root-port'>
<model name='pcie-root-port'/>
<target chassis='7' port='0xd'/>
<alias name='pci.7'/>
<address type='pci' domain='0x0000' bus='0x00' slot='0x01' function='0x5'/>
</controller>
<controller type='pci' index='8' model='pcie-root-port'>
<model name='pcie-root-port'/>
<target chassis='8' port='0xe'/>
<alias name='pci.8'/>
<address type='pci' domain='0x0000' bus='0x00' slot='0x01' function='0x6'/>
</controller>
<controller type='pci' index='9' model='pcie-root-port'>
<model name='pcie-root-port'/>
<target chassis='9' port='0xf'/>
<alias name='pci.9'/>
<address type='pci' domain='0x0000' bus='0x00' slot='0x01' function='0x7'/>
</controller>
<controller type='pci' index='10' model='pcie-root-port'>
<model name='pcie-root-port'/>
<target chassis='10' port='0x10'/>
<alias name='pci.10'/>
<address type='pci' domain='0x0000' bus='0x00' slot='0x02' function='0x0'/>
</controller>
<controller type='virtio-serial' index='0'>
<alias name='virtio-serial0'/>
<address type='pci' domain='0x0000' bus='0x03' slot='0x00' function='0x0'/>
</controller>
<interface type='bridge'>
<mac address='52:54:00:b9:78:55'/>
<source bridge='br0'/>
<target dev='vnet1'/>
<model type='e1000-82545em'/>
<alias name='net0'/>
<address type='pci' domain='0x0000' bus='0x00' slot='0x08' function='0x0'/>
</interface>
<serial type='pty'>
<source path='/dev/pts/1'/>
<target type='isa-serial' port='0'>
<model name='isa-serial'/>
</target>
<alias name='serial0'/>
</serial>
<console type='pty' tty='/dev/pts/1'>
<source path='/dev/pts/1'/>
<target type='serial' port='0'/>
<alias name='serial0'/>
</console>
<channel type='unix'>
<source mode='bind' path='/var/lib/libvirt/qemu/channel/target/domain-11-Big Sur Dev GPU/org.qemu.guest_agent.0'/>
<target type='virtio' name='org.qemu.guest_agent.0' state='connected'/>
<alias name='channel0'/>
<address type='virtio-serial' controller='0' bus='0' port='1'/>
</channel>
<input type='mouse' bus='ps2'>
<alias name='input0'/>
</input>
<input type='keyboard' bus='ps2'>
<alias name='input1'/>
</input>
<hostdev mode='subsystem' type='pci' managed='yes'>
<driver name='vfio'/>
<source>
<address domain='0x0000' bus='0x0a' slot='0x00' function='0x0'/>
</source>
<alias name='hostdev0'/>
<address type='pci' domain='0x0000' bus='0x05' slot='0x00' function='0x0' multifunction='on'/>
</hostdev>
<hostdev mode='subsystem' type='pci' managed='yes'>
<driver name='vfio'/>
<source>
<address domain='0x0000' bus='0x0a' slot='0x00' function='0x1'/>
</source>
<alias name='hostdev1'/>
<address type='pci' domain='0x0000' bus='0x05' slot='0x00' function='0x1'/>
</hostdev>
<hostdev mode='subsystem' type='pci' managed='yes'>
<driver name='vfio'/>
<source>
<address domain='0x0000' bus='0x03' slot='0x00' function='0x0'/>
</source>
<alias name='hostdev2'/>
<address type='pci' domain='0x0000' bus='0x07' slot='0x00' function='0x0'/>
</hostdev>
<hostdev mode='subsystem' type='pci' managed='yes'>
<driver name='vfio'/>
<source>
<address domain='0x0000' bus='0x06' slot='0x00' function='0x0'/>
</source>
<alias name='hostdev3'/>
<address type='pci' domain='0x0000' bus='0x08' slot='0x00' function='0x0'/>
</hostdev>
<hostdev mode='subsystem' type='pci' managed='yes'>
<driver name='vfio'/>
<source>
<address domain='0x0000' bus='0x07' slot='0x00' function='0x0'/>
</source>
<alias name='hostdev4'/>
<address type='pci' domain='0x0000' bus='0x00' slot='0x09' function='0x0'/>
</hostdev>
<hostdev mode='subsystem' type='pci' managed='yes'>
<driver name='vfio'/>
<source>
<address domain='0x0000' bus='0x0c' slot='0x00' function='0x3'/>
</source>
<alias name='hostdev5'/>
<address type='pci' domain='0x0000' bus='0x00' slot='0x06' function='0x0'/>
</hostdev>
<memballoon model='none'/>
</devices>
<seclabel type='dynamic' model='dac' relabel='yes'>
<label>+0:+100</label>
<imagelabel>+0:+100</imagelabel>
</seclabel>
<qemu:commandline>
<qemu:arg value='-set'/>
<qemu:arg value='device.sata0-0-3.rotation_rate=1'/>
<qemu:arg value='-device'/>
<qemu:arg value='isa-applesmc,osk=Ilikecandy'/>
<qemu:arg value='-smbios'/>
<qemu:arg value='type=2'/>
<qemu:arg value='-cpu'/>
<qemu:arg value='Skylake-Client,vendor=GenuineIntel,+hypervisor,-erms,-pcid,-hle,-invpcid,-rtm,kvm=on,+topoext,+svm,+invtsc,+fma,+mmxext,+avx,+avx2,+aes,+xsave,+xsaveopt,+ssse3,+sse4_2,+popcnt,+sse4a,+bmi1,+bmi2,+arat,+abm,+3dnowprefetch,+adx,+clflushopt,+cr8legacy,+fsgsbase,+fxsr_opt,+misalignsse,+movbe,+osvw,+pclmuldq,+pdpe1gb,+rdrand,+rdseed,+rdtscp,+sha-ni,+smap,+smep,+vme,+xgetbv1,+xsavec,+perfctr-core,check'/>
</qemu:commandline>
</domain>