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.
Intel Xeon E3-1270 v6 3.80GHz 4 Cores SR326 LGA1151 CPU Processor
$46.00
Intel - Core i9-12900K Desktop Processor 16 (8P+8E) Cores up to 5.2 GHz Unloc...
$619.99
Intel - Core i7-12700K Desktop Processor 12 (8P+4E) Cores up to 5.0 GHz Unloc...
$419.99
Intel Xeon E5-2697A V4 2.6GHz CPU Processor 16-Core Socket LGA2011 SR2K1
$39.99
Intel Core i5-7600 Quad Core 3.5 GHz 6MB 8 GT/s SR334 LGA1151 CPU
$31.50
AMD Ryzen 7 7800X3D Processor (5 GHz, 8 Cores, Socket AM5) Boxed -...
$320.00
Intel - Core i9-14900K 14th Gen 24-Core 32-Thread - 4.4GHz (6.0GHz Turbo) Soc...
$619.99
Intel Xeon E5-2697 v2 2.7GHz 30M 12-Core LGA2011 CPU Processor SR19H
$27.99
Intel i7-8700 Coffee Lake 3.2GHz 6-Core Max Turbo 4.6GHz Processor
$48.52
Intel Xeon Gold 6238 2.1GHz 30.25MB 22-Core LGA 3647 CPU / Processor ___ SRFPL
$379.99