qemu has supported a usb3/xhci controller for a while, we should enable it for new enough OS. Hans once suggested windows 8 and later but I don't have the reference anymore. It will need some testing. One thing to consider is that by default the qemu xhci controller only has 4 ports, but this is configurable at the qemu level. I imagine with virt-manager we would want to add more ports if there isn't any downside. This bug tracks enabling it that toggle for libvirt: https://bugzilla.redhat.com/show_bug.cgi?id=1271408
Annotations are in libosinfo, and virt-manager has this now: commit 046a242bd4a91472961d9e9eb533629df5661902 Author: Cole Robinson <crobinso> Date: Wed Oct 3 18:53:16 2018 -0400 guest: Use USB3 for x86 qemu if OS supports it Using new annotations in osinfo-db