I think there is no PCIe passthrough for Windows hosts on Virtualbox, and that's required for using CUDA on a VM. You can get graphics acceleration on a VM under any kind of host, but it uses a virtual graphics card from Virtualbox instead of your actual card, so it does not work with CUDA.

This is correct, Linux works much. After for PCIe passthrough in VMs, both Virtualbox and VMware.

Very glad it's now on Windows though! Time to tinker once again.