device: 0.896
other: 0.812
network: 0.557
semantic: 0.506
debug: 0.429
graphic: 0.400
boot: 0.340
KVM: 0.225
PID: 0.211
permissions: 0.205
performance: 0.182
socket: 0.157
vnc: 0.138
files: 0.013

Make -chardev, -serial and others accept stderr like they accept stdio
Additional information:
It's not clear what should happen when the guest tries to read from (instead of write to) the character device. On the other hand, I don't think the specific behavior matters very much.