Virtual Box does provide this feature and its quite easy to configure as well. So I installed Kubuntu as Guest OS on my Windows Host and I wanted to access the host serial port for debugging purposes. I hate to manage two computers for two reasons first is it makes workplace really messy with extra wires and Second is I always need some space to keep items like Power Supplies, Oscilloscopes, Programmers, Debuggers etc. I have Windows XP as primary Operating System, however, I need to work on Linux for lot of hobby projects. As an Embedded Software Engineer serial port access is very critical requirement for me irrespective off which OS I am using and how I am using it (I mean with or without virtualization).
