This is a very advanced advanced solo over a 2 5 1 progression.

The rhythm goes like A D G G. For the solo I go up a fourth from the root and solo over the ascending melodic minors in D E F F. An ascending melodic minor scale is just like the major scale with a flatted 3rd or a minor scale with a major 6 and major 7. This is a very cool way to solo over this progression. Just work out some melody and give it a shot!