Debian hangs on qemu at fb: "switching to bochsdrmfb from simple"

[Robert S <robert.spam.me.senseless@gmail.com>]

I have cloned a running debian system onto a qemu virtual machine for
testing purposes.

If I put a "vga=" statement on the kernel command line (eg. vga=795),
it hangs during bootup.  If I add the 'debug' statement, it hangs
after the following:

[  29.125399] fb: switching to bochsdrmfb from simple

I am using the following command to launch debian:

qemu-system-x86_64 -enable-kvm -net nic,macaddr=xx:xx:xx:xx:xx:xx -net
tap,ifname=tun0,script=no,downscript=no -m 1000 -usbdevice mouse -vnc
192.168.0.40:0 -monitor /dev/stderr $@

I can fix this by adding "vga=normal" to the command line, but I'd
like to have more control over the screen resolution.

Can somebody propose a fix?