Is it ok to tell my boss @ work, that I'm heavily involved with real estate?

[Henri Meli]

I have a 9-6 job and recently, my company went from cubicles to open space office set-ups. I seat pretty much next to my boss now. As I grow my business more and more, I have found myself getting calls from brokers, insurance, agents, bankers, ... etc in the middle of the day during meetings and such (on my cellphone, nothing on my business phone). 

A few months ago, I had mentioned it to my co-workers that I do have a volume of real estate investments and was looking to add more. The information might have trickled up to my boss and in the last couple of 1x1 sessions with my boss, he tried to ask me all the other "interesting things" I do outside of work. Although my boss seems like a "nice and reasonable" person, I don't want him to know any of my personal business.

Does your manager @ work know you are an investor? Have you had that conversation with them? Just curious how various folks have handled this situation. If you were a manager at your job, how would you handle this situation?