After I program an IBERT GTH bitfile on a KCU105 board, and create the link with Near end PMA Loopback and set "LOGIC.RESETFSM_OVERRIDE= 1" and "PORT.GTTXRESET = 1", I see that "PORT.GTTXRESET" and "LOGIC.RESETFSM_OVERRIDE" values are toggling between 0 and 1 in the dashboard.
Because of this issue, Vivado hangs while trying to change the reset, or any other properties in the GUI.
To work around this issue, set GTTXRESET and RESETFSM_OVERRIDE back to 0.
As soon as both of the signals are set back to zero, the link status signal is set back to High.
Click on the TXRESET & RXRESET buttons in the SIO GUI to get clean data.
If the user is setting GTTXRESET and RESETFSM_OVERRIDE to 1, it is expected that after some time user will set back these signals to 0 to get the link back.