Air carrier Captain reported smoke coming from the air vents in the flight deck during cruise. Flight returned to departure airport and maintenance determined smoke was caused by a pack.

Narrative

We departed ZZZ XXC on the ZZZZZ [departure]. Everything was normal as we reached our cruise altitude of 17;000ft. We leveled off and completed the cruise checklist; shortly after we began seeing white smoke coming from the air vents in flightdeck.We completed the QRC procedure for smoke but decided not to don oxygen because the smoke light was not causing issues breathing or seeing. And I felt the difficulty communicating would outweigh the benefit at that point.During this time we requested priority handling and told ATC we needed to return to ZZZ. I ran the QRH and the FO took controls and radio. We completed the associated QRH Procedure and descended to 10;000ft. Once we had done so the smoke dissipated. I communicated with the FA; passengers and dispatch; while the FO flew us in on the ZZZZZ1 arrival for XXR.FA stated the she could smell smoke but it seemed to be contained to the flightdeck and passengers were not affected.When we landed we pulled off the runway and were inspected by the airport fire vehicles; they then followed us to our gate where we deplaned normally.Maintenance later stated it was Pack 1 that had caused the smoke