Hi Zachary,
Child(Genode::Env& env, Child_policy::Name name) : _env(env), _name(name) { }
I have no experience with the parent/child interfaces, my naïve first thought would be to add tracing (Genode::log()) in the body of the constructor above, at least to "bracket" the output sent to Qemu's virtual serial port. If all else fails, you could even "go down the rabbit hole" and add tracing to the Genode code itself (following down the chain of classes and methods), I learned quite a bit of the system this way myself, though it's of course time consuming.
Talking of logging, you might want to post the logging output from Qemu here, it could be a starting point for those on the list with better knowledge and odds to help you.
Cedric
As I said previously, this is my first attempt at creating a Genode system from scratch. Any feedback you may have is greatly appreciated (even if it is not directly related to the issue at hand).
[1] https://gist.github.com/zgzollers/397f56b66179f3276e048be8a8a7a543