Looking for nested virtualization for Proxmox testing

Nested virtualization for Proxmox testing

I need to test Proxmox clusters without buying bare metal. KVM inside KVM, basically. Most providers block `vmx` or `svm` in their KVM flags—understandable, but annoying for labs.

Tested so far:
- Vultr: flat no, "nested virt not supported"
- Hetzner: no response to ticket about cpu flags
- Contabo: YES, with specific flag. Need to enable "Expose Hardware-Assisted Virtualization" in their panel, then add `host` cpu type in VM config. Verified with `egrep -c 'vmx|svm' /proc/cpuinfo` inside guest.

Working config for anyone who needs it:
CPU type: host
Flags: +vmx (or +svm for AMD)
Machine: q35

Propagation of this knowledge: please check your resolver before saying it doesn't work. I traced routes to prove the nested guest was actually running on the nested host, not faked.

Since 2 days I test with Proxmox inside Proxmox, lol. It is possible to do that? Yes, with the flag you say. I have try on Hostinger before but no, they block. Mdr.

My config is same, but I add `kvm=off` for one test and it break everything. Bref, your guide is good, thank you. 😅