In Virginia you are not required to retreat in your house or public if you did not invite the attack. Exchanging words is inviting. Only if you indicate by 'acts and words' that you in no way desire to continue the altercation and are then pursued can you escalate the fight.
You must feel in danger of death or grievous bodily harm to yourself or others to use deadly force. A 'resonable man under the circumstances' rule applies.
Any use of deadly force is very likely to result in a protracted legal battle, particulalry in the more liberal areas of the state (Nothern Va, Richmond).
Virginia has justifiable and excusable case law. Justifiable is basically unprovoked, excusable often involves some action on the defenders part and an attacker that does not desist despite warnings to break off and a 'acts and words' indicating you do not desire to continue the fight.
Like many states, there are no stuatuates authorizing deadly force, only case law defining when its use has been found justifiable or excusable.
The Virginia Gubn Owners Guide has a pretty good summary of the law, both statuate and case.