Ivan can tell the amount of effort David is putting towards not hurting him, and finds himself making encouraging noises in the back of his throat to reassure him. It's fine, he can take this, David needn't be so careful; and for a (professionally) horrifying moment the sound he makes changes into one of genuine pleasure. There's no need to let David know that, and hey -- everyone's got stories about those times they got carried away.

Refocusing, Ivan lets David set the pace, sucking, curling his tongue around him and over with every thrust he makes into his mouth. One of his hands goes to the other man's hips, massaging the soft skin there in what Ivan hopes is a clear sign for the other man to go deeper if he wants to. Ivan will manage just fine.