I received some help with qemu on the NetBSD mailing lists, if I add -monitor stdio to the qemu command line then I get the monitor command line in the xterm where I started qemu. This allows me to send key events to the running emulation. I wanted this so I could drop NetBSD to ddb in qemu so I could tweak variables in the kernel. With the added command args I can now do this.
I wanted ddb so I could turn on the UVM history printing, I tried running with the history printing on as a default but this produces so much output it has a severe performance impact and I was never sure what was happening because everything scrolled up the screen so fast. So, I thought that I could disable the printing by default and just enable it before I run my tests. Hence the need for ddb. Unfortunately, even enabling the UVM history printing just prior to running my tests still produces so much output that it does not help. So, I will try just enabling the printing in the veriexec page routines to try and keep the amount of information manageable.