My kernel line is (I disable the spectr/meltdown mitigations so ignore those parts):
root=/dev/mapper/ssd-arch--root rw intel_iommu=on iommu=pt i915.enable_guc=3 i915.disable_power_well=0 i915.enable_psr=1 i915.enable_fbc=1 i915.enable_rc6=1 pci=nomsi,noaer pti=off spectre_v2=off l1tf=off nospec_store_bypass_disable no_stf_barrier
The XML for the VM I configured in virt-manager can be found here:I don't think has any significant modifications. Eventually I want to switch over to using the newer q35 architecture. The only issues I've had with the VM are some audio glitches in some games and it has recently had issues with hugepages so I've had to disable that.