[throwaway2048]

xen is over 100k lines of code, not counting the kind of interfaces software exposes using its APIs, and stuff like drivers.

its not small

[hershel]

You don't need to review all that code. From the qubes architecture document:

"it is possible to move all the drivers and driver backends out of Dom0. The same is true for moving the IO Device Emulator (ioemu) out of Dom0."