Hi, we see here a confusing problem. A college reboots/shutdown his VMs for maintenance. After that he starts the VMs (~20), but one of them throws following error:

VM <name> is down with error. Exit message: internal error: Unknown CPU-Model SandyBridge,+spec-ctrl

All nodes of the clusters are reporting:

CPU Type: Intel SandyBridge IBRS Family

And the cluster is configured with:

Cluster CPU Type: Intel SandyBridge IBRS Family

My quick fix for the vm was, that I used a specific (not the cluster default) CPU-Model without the spectre/meltdown mitigation:

Guest CPU Type: SandyBridge

I've also tried to select manually "SandyBridge,+spec-ctrl". But when I do this the wizard blocks and surround the field with a red border (see picture in the attachment). Any idea? Greeting Tobias