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.
HP Workstation Z640 2x Xeon E5-2623V4 32GB Ram 2x 256GB SSD Quadro 2000 Linux GA
$249.99
HP Workstation Z640 2x Xeon E5-2623V4 32GB Ram Dual 256GB SSD K420 Linux GA
$214.98
Dell Precision 5810 Workstation Xeon E5-1650 6C 3.5GHz 16GB 500GB Win10 K2200
$115.94
Apple MAC Pro A1481 Late 2013 Xeon Quad-Core 3.7GHz 32GB 1TB SSD FirePro D300
$285.00
Dell Intel® Xeon® Processor E5-2698 v4 Lightly Used
$64.00
SR1XP Intel Xeon E5-2680 v3 12 Core 30MB 2.5GHz LGA 2011-3 Grade A Processor
$3.96
Genuine Intel Xeon E5-2680V4 2.40Ghz 14-Core 35MB LGA2011 CPU P/N: SR2N7
$14.99
Intel Xeon E5-2690 v2 10-Core 3.0GHz 25M 8GTs LGA2011 Server CPU Processor SR1A5
$14.99
Intel Xeon E5-2697 v4 2.3GHz 18-Core Processor CPU LGA2011 SR2JV
$49.99
Cisco UCS C220 M4 1x Xeon E5-2667 V4 3.20GHZ 128GB DDR4-2400MHZ 2x 770W AC PSU
$129.99