Try
http://local.live.com/ to look up route options.
The quickest (and among the shortest) route is via Mahbubnagar > Raichur > Dharwad > Hubli, but road conditions during this season may not be the best after Raichur. You'd do well to ask around on road conditions.
An alternate route via Zaheerabad > Sholapur > Belgaum will add ~100 km to your distance, but is said to be a lot better.
Driving time can be between 12-16 hours depending on the road conditions and your pace, so you may want to halt somewhere halfway if that is too much to do at a stretch.