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.
HGST Ultrastar HE10 HUH721010ALE600 10TB SATA 6Gb/s 7200RPM 3.5" Enterprise HDD
$74.99
WD4000FYYZ Western Digital 4TB SATA 3.5 Hard Drive
$149.99
WF12F DELL 1TB 7.2K 6GBPS SATA 2.5'' HDD HARD DRIVE ST91000640NS 0WF12F
$25.00
Western Digital WD60PURZ 6TB Hard Drive SATA6 Gb/s 64MB Cache 3.5 Inch
$109.99
HGST Ultrastar DC HC520 12TB SATA 6Gb 256MB 3.5" Enterprise HDD- HUH721212ALE601
$82.99
Seagate Exos 7E10 ST2000NM000B 2TB 7200RPM SATA 6.0Gb/s 3.5" Internal Hard Drive
$29.99
2 PACK Seagate ST1000LM035 Mobile HDD 1TB 2.5" SATA III Laptop Hard Drive
$27.25
TOSHIBA MD04ABA400V 4TB 128MB Cache SATA 6. 0Gb/s 3. 5"
$18.00
WD HDD Ultrastar DC HC520 HUH721212AL4205 12TB 3.5" SAS Server Hard Disk Drive
$45.23
HDD 3.5" SATA Hard Drive with Windows 7/Win 10 Installed Legacy
$35.99