Hello,
I experiences similar problems using the exact same Qemu version as yours. To work around it, I first instructed Qemu to use the SDL back end by adding the following line to the Genode build configuration at '<build-dir>/etc/build.conf':
QEMU_OPT += -display sdl
But that was not enough to fix the bugged user input. I also had to set the environment variable SDL_VIDEO_X11_DGAMOUSE to 0.
export SDL_VIDEO_X11_DGAMOUSE=0
This fixed the problem for me. But I still have not investigated what strange kind of events Qemu is delivering by default now. The events seem to confuse the PS/2 driver completely.
Cheers Norman