I upgraded to ProxMox 6.0 and to my dismay my Windows VM suddenly began receiving the dreaded Code 43 error. After much digging I finally found this post on the ProxMox forums which outlines what needs to happen.
In my case, all I needed to do was tweak my machine type. There is no GUI option to do this, so it had to be done in the command line:
qm set <VM_ID> -machine pc-q35-3.1
That was all it took!
The forum also suggested a few other things if that didn’t work. I didn’t end up needing them but I’ll put them here in case it’s helpful:
Add args to your VM config file:
args: -cpu 'host,+kvm_pv_unhalt,+kvm_pv_eoi,hv_vendor_id=NV43FIX,kvm=off'
Add a few options to the CPU line:
With the above settings I also discovered there is no need to have x-vga=on anymore. This allows you to have both the regular VM console and your graphics card if you so desire.