The Mi A1 was the first Android One device from Xiaomi, meaning it ran completely stock Android. It turned out to be an excellent phone, and Xiaomi promised it would receive Oreo before the end of 2017. It looks like the company just barely delivered on that promise, because Android 8.0 is now rolling out to the device.
Xiaomi has been testing Oreo on the A1 through a public beta test for at least a week.
Android 8.0 Oreo rolling out to Xiaomi Mi A1 was written by the awesome team at Android Police.