Silva got a lot of shit for being knocked down by Bisping and people said his chin was done. He didn't go out like Rockhold did so maybe his chin isn't as bad as people said. Instead it should be Silva just got caught really good and did well to recover from it that quick.
Once he got caught he went for the upkick right away it wasn't like he was out 
Silva never had necessarily a granite chin.
He had amazinf reflexes and was able to roll with the punches.. Now that his reflex/speed is at 60% he gets hit a lot more. He has a decent chin, but his ability to roll and see it coming before made it look way stronger.