Two Proxmox VE 9 Defaults You Might Not Have: Hyper-V Enlightenments and CPU Microcode
Proxmox VE 9 turns on Hyper-V enlightenments for Fisher-Price OS (Windows) guests and installs CPU microcode on new hosts, but only if the VM was given a Microsoft Windows OS type and the host came from the 9.x installer. This covers what the enlightenments do, the exact rules qemu-server uses to pick them (measured on a live 9.2 host), why machine version pinning keeps older VMs off the July 2026 hv-evmcs fix, the pve-qemu-kvm build that fix needs and what each QEMU release since 10.0 fixed for those guests, why they belong on q35 and never i440fx (which the wizard still hands most of them), the two flags you can set by hand, how to prove what a VM is running, where microcode comes from (board firmware, Debian and Proxmox’s own repository), why an upgraded host has none (with an Intel node four Intel releases behind as the example), the initramfs rebuild that installing it triggers and the older kernels that rebuild misses, the Zen 5 RDSEED failure that follows, enabling it, a rolling reboot across a Ceph cluster, and rolling back a bad update.