"All GEN failure" is not specifically addressed in our QRH, but the Standby Power System is addressed at length.
You would individually attempt to reset the generators (we are allowed only 1 attempt on each one). When that fails, you will have to deal with the airplane on Standby Power only, which is essentially the Capt's instruments (left PFD, ND, FMC, ADC, Transponder, EIU, FMS-CDU, ILS, VOR; Primary EICAS, flight control components). Find a place to land within 30 minutes!