How can I ask WH questions for a sentence that contains Passive Voice? What is the rule for it?

The example of sentence is

A feast had been prepared at the hotel La Reserve to celebrate the engagement of Edmond and Mercedes.

I'd like to ask this question:

Where had a feast been prepared?

Is it correct?

It's perfectly normal to ask 'wh' questions in a passive voice. Consider:

I entered La Reserve and found the dining room set in a formal arrangement for many people. I asked a waiter "For whom has a feast been prepared?"

The manager of La Reserve came back from a two day break and the chef said "We have been working on a feast all day". The manager asked "Why has a feast been prepared?"

I arrived at La Reserve and was told "We have prepared a feast in your honour". I answered "Thank you, what sort of food has been prepared?"

You can do this for any "wh" word so long as the context is appropriate, no special rules are necessary.