Don't forget that the GSV is a scanned instruction - it does nothing if not scanned.
If you have a major fault, the logic stops, and therefore the GSV will not execute. The HMI would not read the value.
I find it best to just monitor the communication with a handshake, then if an alarm comes in, someone goes online to interrogate the reason for the disruption.
Also realize that when the major fault is cleared, the process will resume. Be sure that you have a fault routine that sets the process in a safe mode.