No weakening should be done near the top or bottom edge (which is worst in this case). If it's near support (wall), it will usually work fine.
If you make 3-4 holes (max 50 mm) fairly close to the wall (30-50 cm) centered in the floor joist with approximately the same distance between them as the hole diameter, you will, in practice, not weaken the construction at all. Reinforcements are not needed.
