Error when starting KVM guest with more than 2 serial ports on RHEL 6

Issue

• Error when starting KVM guest with more than 2 serial ports on RHEL 6

With a RHEL 6 KVM guest containing:

<serial type='pty'>
  <target port='0'/>
</serial>
<serial type='file'>
  <source path='/tmp/rhel6-3-sparse-tst.log'/>
  <target port='1'/>
</serial>
<serial type='pty'>
  <target port='2'/>
</serial>
<console type='pty'>
  <target type='serial' port='0'/>
</console>

On a RHEL 6.3 KVM host the error resembles something like the following:

error: internal error process exited while connecting to monitor: char device redirected to /dev/pts/23
char device redirected to /dev/pts/37
isa irq 4 already assigned