When I was in the motor trade (a long time ago) white smoke was usually caused by brake fluid being drawn into the engine and burnt. This was when the servo had the master cylinder mounted on them and the brake pedal acted directly on the servo.
Faulty seals in the master cylinder allowed hydraulic fluid to drain back into vacuum servo and then it was sucked into into inlet manifold via the vacuum hose.
Not certain what system you have on your car but it can't hurt to just check the fluid level, if nothing else it serves to eliminate a possible cause.