I have a 2009 Mac Pro, which has been upgraded to a MacPro5,1. It's currently running macOS Sierra. I was going to upgrade it High Sierra, but the High Sierra installer said it needs to first update the firmware and asked me to proceed in doing that.
I'm nervous to allow this to happen since the firmware was already upgraded from a MacPro4,1 to a MacPro5,1.
Also, I'm running a flash NVIDIA GTX 980, which has the boot support. I'm afraid this might cause problems as well.
Are there any known issues or conflicts with my configuration or similar configuration when upgrading to High Sierra?