I had pve 7.x running on a spare laptop that I had kicking around. Everything was working well until the upgrade. Until I realized that I couldn't spin up a new vm after it's creation. Took me a minute to realized that my issue was that I chose the default CPU type (x86-64-v2-AES). I then changed that to x86-64-v2. Then all was well in the world. At least my world that is.