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.
IBM Power S822 8284-22A 12SFF Power8 3.89GHz 6Core 64GB RAM No HDD Server System
$359.99
IBM System X3250 M3 Server 8GB RAM Intel Xeon x3440 2.53ghz (NO HDD)
$36.53
IBM Server System X3100 M4 | Xeon @ 3.10 Ghz | 8GB | 250GB HDD No OS (IG-PC26)
$96.01
$4750.00
IBM System x3550 M3 Dual Intel Xeon X5650 @2.67GHz 32GB RAM No HDD
$74.50
IBM Power8 12-Core 3.52GHz Server Processor 00KV829
$59.96
$16000.00
IBM mainframe server cpu IBM93 vintage cpu collector's item
$125.99
IBM x3650 M4 2x Xeon E5-2670 2.6ghz 16-Core / 64GB / M5110e / 2x PSU
$229.99
IBM 5362 Server System/36 60MB HDD With Manuals
$7700.00