I tested the build linked in Comment 1 with RHEL-6.4 GA version of libvirt and everything seems to work fine.

I tested: monitor, console, serial ports, spice agent channel and guest agent channel. This should cover the most basic usage of chardevs of qemu by libvirt.

The monitor works fine under normal conditions and slight load. The console and serial ports work fine with PTY backend and TCP backend both under heavy load and normal usage. The spice agent channel is working fine. The guest agent channel with unix socket backend works well and under heavy load too.

Even with no clients reading the guest behaved fine and the channels worked after reconnecting the reader.

I'm moving this now to ON_QA as it's a test-only bug to incorporate into standard testing cycle.

Thanks for testing!  Your testing is indeed encouraging, allowing us to proceed with pushing the patches forward.

The qemu patches are not yet part of an official build, QE should wait till that happens for testing.  I will update this bug when qemu gets all the patches in.

qemu patches are available in the official builds starting from qemu-kvm-0.12.1.2-2.368.el6

Verify this bug with libvirt-0.10.2-24.el6.x86_64 and qemu-kvm-rhev-0.12.1.2-2.401.el6.x86_64. It seems everything is working well, so change the status to "verify".

Steps:
1. "socket-virtserialport", edit the guest xml like the following one:
......
<controller type='virtio-serial' index='0'/>
<channel type='unix'>
      <source mode='bind' path='/var/lib/libvirt/qemu/b.agent'/>
      <target type='virtio' name='org.qemu.guest_agent.0'/>
    </channel>
......
2. start the geust, then transfer data from the geust to host and back.
Send data out from the guest: 
        # echo a > /dev/vport0p0
Receive data in the host: 
        # nc -U /tmp/guestfwd
        a
Send data from host: 
        # echo a | nc -U /tmp/guestfwd
Receive data in the guest: 
        # cat /dev/vport0p0


3. "socket-virtconsole" type, edit the guest xml like the following one:
......
<controller type='virtio-serial' index='0'/>
    <console type='unix'>
      <source mode='bind' path='/var/lib/libvirt/qemu/b.sock'/>
      <target type='virtio' port='0'/>
    </console>
......
4. try to communicate between the guest and host.
In the guest:  # agetty /dev/hvc0 9600 vt100
In the host:
       install socat tool.
               # ./socat /var/lib/libvirt/qemu/b.sock -
 
    you will see the login promt list this:
 
        Red Hat Enterprise Linux Server release 6.0 (Santiago)
        Kernel 2.6.32-71.el6.x86_64 on an x86_64
 
        localhost.localdomain login: redhat
        redhat
        password: redhat

5. "pty-virtserialport", edit the guest xml like the following one:
 <controller type='virtio-serial' index='0'/>
        <channel type='pty'>
          <target type='virtio' name='org.linux-kvm.port.1'/>
    </channel>
6, try to communicate between the guest and host.
In the guest, send data:
        # echo a > /dev/vport0p0
In the host to receive the data: 
        # cat /dev/pts/6
        a
In the host to send out a data: 
        # echo "This is from host" > /dev/pts/6
In the guest, receive the data: 
        # cat /dev/vport0p0
        This is from host

TestOnly bug for 6.5