[anonymousiam]

Back before libvirt made it trivial, I used QEMU/KVM directly to map PCI devices to VMs. It's a little tricky because you must first unmap the device from the host/hypervisor, and you need to unmap the whole bus that the device is on. So if there are other PCI devices on the same bus as that device you want to map, they must all go along, which is often impossible for things like the USB controller for your keyboard/mouse.

These days, instead of crafting a custom script to launch QEMU/KVM for PCI mapping, it's just a few clicks in virt-manager. Note that the first time you launch a VM with a mapped PCI device, the launch will often fail with an error, but it will work on a subsequent retry and thereafter.

Also, I've tinkered with lots of VMs over the past 15 years and I've NEVER had a need for more than 14 buses. Hopefully I never will.