I remember seeing a bug in get_hv_cpuid on the KVM mailing list at some point, it should have been fixed in newer kernels though. That also explains why switching to "Linux" fixes it, since that disables the Hyper-V extensions for the VM.Dec 5 09:17:07 node3 kernel: [3236224.935997] CPU: 26 PID: 3030113 Comm: kvm Tainted: P D O 5.0.21-3-pve #1
Dec 5 09:17:07 node3 kernel: [3236224.945437] Call Trace:
Dec 5 09:17:07 node3 kernel: [3236224.946020] kvm_vcpu_ioctl_get_hv_cpuid+0x44/0x220 [kvm]
Try rebooting the node to load the new 5.3 kernel included in 6.1, then your VM should run with OS type "Windows" as well.