Cove Lighting refers to lighting in a suspended ceiling where the lighting itself points up and is then reflected by the ceiling into the scene.
Here is a model with cove lighting after 30 rendering passes. The model has a single light applied to the entire upward facing surface on top of the recessed area of the ceiling. After 30 passes the lighting in the room is somewhat balanced, but still the lighting above the ceiling shows the effects of the individual lights. This will improve with additional rendering passes.
After 200 passes, the lighting is fairly smooth.