I have VMware Workstation running on Ubuntu host with a Ubuntu Guest. Is it possible to directly access the GPU from the VM?
I want to run CUDA on the VM
It isn't unless nVidia provides a VMware-compatible paravirtualized driver for that purpose.
This discussion on the nVidia forums explains why.
Now, newer CPUs and chipsets support "IOMMU", which could serve the similar function as "PCI-E passthrough" that they discuss on that forum. However, this still requires support and cooperation from both VMware's paravirtualized drivers and nVidia's drivers, which does not exist yet.
If you are ready to use Xen instead of VMware Workstation, you can try out Xen VGA Passthrough and see if your hardware configuration is supported. This would give you full control over the graphic card in the VM.
Here is an example of what you can accomplish: http://www.youtube.com/watch?v=Gtmwnx-k2qg