It is flawed to 'roll back' changes. Instead, those changes have to have never existed. Otherwise, there is a short window of time when the cache-visible side

It is flawed to 'roll back' changes. Instead, those changes have to have never existed. Otherwise, there is a short window of time when the cache-visible side-effects have happened, and haven't been rolled back yet, and the attacker can see them (due to preemption, due to hyperthreading, due to running in another core etc).