ttyS0 pass through in guest running in KVM doesn't work and eventually hangs

[Obrouni]

Running a up to date Jaunty server Install and using KVM to host virtual machines. One of the guests has the ttyS0 of the host passed through to it with a weather station connected to the host port:-

<serial type='dev'>
<source path='/dev/ttyS0'/>
<target port='1'/>
</serial>

The serial port is passed through and is correctly detected in the guest. However the weather station software cannot communicate with the weather station device. Further more after about 15-20 minutes the guest becomes unresponsive and I cannot even view the console through virt-manager or shut it down with virsh. I am then forced to kill it with a "kill -9".

I believe that a bug has already been reported and a patch supplied in January of this year, as it seems to describe my symptoms exactly:-

http://thread.gmane.org/gmane.comp.emulators.kvm.devel/27809

[Jaap Versteegh (j-r-versteegh)]

I have what I think is the same problem. Windows XP guest on jaunty x86_64 host:
$ kvm -hda windows_xp.qcow2 -boot c -m 1024 -localtime -serial /dev/ttyS0

Setting the baudrate on Windows also modifies the baudrate on the jaunty host, but no data is transferred.

When I run:
$ qemu -hda windows_xp.qcow2 -boot c -m 1024 -localtime -serial /dev/ttyS0
Could not open '/dev/kqemu' - QEMU acceleration layer not activated: Permission denied

all works well, though very slowly !

[Dustin Kirkland  (kirkland)]

Thanks for the bug report and investigation. This should be fixed in Karmic, as soon as I merge the new qemu-kvm package.

If you'd like to test the pristine daily upstream build, you can try the qemu-kvm package in the following PPA:
 * https://edge.launchpad.net/~qemu/+archive/ppa

Note, these packages are for testing *only*, and are substantially unsupported ;-)

:-Dustin