CentOS virt - Jul 2011 - Send magic-sysrq from virtual serial console?

I am using CentOS 5.6 as a KVM host.   My guests are running CentOS
5.6 with the only console being a virtual serial console.  The guests
are configured so magic-sysreq can be used to debug kernel issues.


However, in order to send magic-sysrq from a serial port, I need to
send a break.   How does one send a break on the virtual console
serial port provided by KVM/libvirt to guests?

Thanks,
   David