My knuckles lay against the child’s blue jeans. She was barefooted; her toenails showed remnants of cherry-red polish and there was a bit of adhesive tape across her big toe; and, God, what would I not have given to kiss then and there those delicate-boned, long-toed, monkeyish feet!
(Lolita, Vladimir Nabokov)
It’s hard to find out the proper account for above ‘what’ in dictionaries. What does ‘what’ mean: does it mean ‘on what reason’?