Jamie Foxx knows silence is golden when it comes to talking about Katie Holmes ... but he still wants everyone to know they're all good as a couple.

Jamie was in Malibu Wednesday morning when a photog asked him all about Katie and their very first PDA on the beach. TMZ posted the first pics ... showing them strolling on Monday -- and, as we reported ... the relationship has been the worst-kept secret for years.

So, why go public now and what does her ex and his pal, Tom Cruise, think?

Jamie kept his response brief ... and mostly nonverbal.