Comment 39 for bug 886521

Stefan,

Yes, the unplug "feature" was added in Xen between 3.3 and 3.4 (the magic port to support it), and it, um, somewhat lacks OS friendliness. The config file to achieve desired results is also non-obvious. It generates significant problems in moving VMs from Xen3 to Xen4, and also upgrading domU kernels (for instance, an upgrade from Lucid/Maverick to Natty/Oneiric/Precise will cause the emulated disk to disappear as well as the PV disk to appear under a different name, which will cause a reboot failure). In my opinion, it would have been better to leave the emulated disk there, possibly doing something to lock it (so it couldn't be mounted) or remove it if the PV disk is opened. It would also have been useful to give more control to the dom0 in what might and might not be unplugged. But "we are where we are".

As far as having a 3.0 kernel which accesses emulated disks but not PV disks, you can do this by disabling the whole of the PCI system, either from xen.conf or by blacklisting the module, or possibly by one of the command line boot scripts. But of course this will affect your net drivers too.

Alex