In general, how many days do you live and work in Virginia and how many days in PA?
As Hal_Al mentioned, VA and PA do have a reciprocal agreement -- an agreement between two states that allows residents of one state to request exemption from tax withholding in the other (reciprocal) state. This can save you the trouble of having to file multiple state returns.
However, depending on the amount of time you spend in PA, you may be considered dual residents and subject to the North Eastern States Tax Officials Association Cooperative Agreement (NESTOA Agreement).
