category: reference
tags: [infrastructure, proxmox, vps]
last_updated: 2026-03-15
confidence: high

Proxmox CPU Type Issue

Problem

The robot.wtf VM uses the default kvm64 CPU type in Proxmox, which doesn't expose SSE4.1, SSE4.2, or POPCNT flags. numpy 2.4+ requires these (X86_V2 baseline) and refuses to import.

Current workaround

numpy<2.4.0 pinned in requirements.txt. This works but freezes numpy on an older version.

Proper fix

Change the Proxmox VM CPU type from kvm64 to host. This passes through the physical host's CPU features to the guest. Requires a VM reboot.

Tradeoff: CPU type host breaks Proxmox live migration between hosts with different CPUs. If this VM doesn't need live migration (it doesn't currently), host is the better choice.

To apply: In Proxmox UI -> VM -> Hardware -> Processor -> Type -> host. Or edit /etc/pve/qemu-server/{vmid}.conf and set cpu: host. Then reboot the VM.

After changing, the numpy pin can be removed from requirements.txt.