zerovar parent
Can something like this be used to, say, build emulators for different game consoles? And do the popular emulators use this as a building block? Asking this as someone whose only experience with emulation and virtualization is running games on VisualBoyAdvance and running Ubuntu on VirtualBox
Yes:
Are both original Xbox emulators built off of QEMU (Xemu is a fork of XQEMU). I've only used Xemu, but performance was pretty good for the games I tried on it (it doesn't have a way to upscale rendering yet though).
Good news! Upscaling is in work but buggy right now.
You could build emulators for consoles, but QEMU is not cycle accurate. Meaning some operations may finish faster or slower than they would on the original console. Some games may rely on that timing for things like physics engines and break in weird ways.
its not really meant for that, but there wouldn't be anything to stop someone from creating the hardware emulation, as far as I know. Still, purpose-built console emulator software is sure to be far better for the task.
You're looking for MESS: http://mess.redump.net/