Blazing salvo says:
Blazing Salvo deals 3 damage to target creature unless that creature's controller has Blazing Salvo deal 5 damage to him or her
So I deal 3 damage to target creature, bt what does it mean "creature's controller has Blazing Salvo"? Does he need to reveal it in his hand to prevent the 5 damage to him, or can he have it in graveyard or library?