We built some internal tooling to help manage the hosts. Once a host is onboarded onto it, it's a few button clicks on an internal dashboard to provision a QEMU VM. We made a custom ansible inventory plugin so we can manage these VMs the same as we do machines on GCP.

The host runs a custom daemon that programs FRR (an OSS routing stack), so that it advertises addresses assigned to a VM to the rest of the cluster via BGP. So zero config of network switches, etc... required after initial setup.

We'll blog about this system at some point in the coming months.