For several years I have run both the Knoppix ISO-image and disk-based versions under kvm for installs, maintenance etc. The basic method works for 8.3 too, but only as far as the first flash install.
Klaus K has made Knoppix more "fool-proof" to run under kvm by restricting it to read-only mode. For many users, that is clearly a feature: You may run your ordinary Knoppix install under kvm so it functions as both host and guest at once, but if persistent store is involved, and the host and the guest instances perform different updates to that, then what?
It is only a question of time until the file system is corrupted - it is easy to imagine that prof. Knopper has introduced this restriction from experiences with broken systems.
The bug is that it doesn't stop there. If you run different copies of Knoppix on different partitions, or run Knoppix under another OS variety, even another version of Knoppix, the only thing to be careful about is that the partition where the persistent store of the VM resides is not writable by other OS'es. But don't try to explain that to Knoppix 8.3. It only checks whether it is run under kvm, and in that case, the system is mounted read-only. Which kind of blocks many important uses of Knoppix images.
While the default behaviour is "correct", there must be a cheatcode for disabling it, e.g. VIRTWRITE. I guess specialists on minirt.gz should not have too much problems rolling their own, but this is a general issue, so for me it belongs in Knopper-land proper.
Cisco IE-3000-8TC Industrial Ethernet 8 Ports Managed Switch 1 Year Warranty
$114.00
HP ProCurve 4108gl J4865A Modular Network Switch
$119.99
Cisco Nexus 48-Port 10G SFP+ Switch N9K-9396PX w/ 9K-M12PQ 12-Port 40G QSFP
$249.99
Juniper EX4300-24T Layer 3 24 Ports Manageable Ethernet Switch 1 Year Warranty
$195.00
HP 2530-48G 48 Port Gigabit Ethernet Network Switch J9775A
$30.95
New Linksys SE3005 5-port Gigabit Ethernet Switch
$18.99
New 10/100 Mbps 8 Ports Fast Ethernet LAN Desktop RJ45 Network Switch Hub
$11.49
HP ProCurve 2530-24G J9776A 24 Port Gigabit Ethernet Managed Network Switch
$34.99
Juniper Networks EX3300-48P 48-Port PoE+ 4x SFP+ Network Switch w/ Power Cord
$43.95
HP Aruba 2530-8G-PoE+ 8x PoE+ RJ45 2x SFP Gigabit Switch J9774A No AC Adapter
$37.99