Two things I think may be on the table:
- Kim to inform Xi about the recent NK/SK summit. President Moon must have said things and passed something from Trump. Kim want to share and coordinate with Xi before the possible summit with Trump.
- Trump said something "tough" recently (few days ago), Kim may need some advice on his measured reaction. A reaction that does not show weakness, but neither fueling the fire (therefor derail the track). Once committed and determined to seek a settlement, Kim will act much less reckless (he was NOT really reckless before either).