This feature is not officially supported / tested, and may not work at all.
Contact your VM vendor for more information.
The cifX Device Driver is a hardware driver and requires physical access to the CIFX card. This can be achieved in some virtualization software by using PCI pass-through technology (i.e. VT-D).
The CIFX PCI configuration (PCI_COMMON_CONFIG) is lost during driver startup, as a hardware reset is executed, and must be re-written by the CIFX device driver. This works well when running a plain windows system, but as virtual environment usually emulate PCI configuration accesses, RAM-based CIFX devices cannot be used in this environment.
You will need to ask your VM vendor for more information (if a guest system may physically re-write PCI common config area). If not, a RAM based CIFX card cannot be used in these systems.
Some open-source virtualization environments may be patched to re-write the PCI common config if the guest writes these areas, so the hardware registers of the CIFX card will be restored. In these cases a RAM based CIFX device can be used in the guest system.