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.
Supermicro Server Tower Xeon BOOTS E5-2620 v4 2.10GHz 64GB RAM NO HDD NO OS
$199.99
2U 12 Bay SAS3 SuperMicro Server 6028U-TR4T+ W/ X10DRU-i+ Barebone 12 Caddy RAIL
$299.00
HP PROLIANT MICROSERVER MICRO SERVER HSTNS-5151 T4 Used.
$45.00
HP ProLiant Xeon E3-1220L V2 16 GB RAM 2.30 GHz MicroServer Gen8 NO DRIVES
$174.99
HPE PROLIANT MICROSERVER GEN10 PLUS MICRO TOWER SERVER - USED
$550.00
SuperMicro Server 505-2 Intel Atom 2.4GHz 8GB RAM SYS-5018A-FTN4 1U Rackmount
$202.49
HPE Proliant Microserver Gen10 X3421 Perf AMS, P03698-S01, 16GB Ram
$299.00
HP ProLiant HSTNS-5151 Micro Server 8GB RAM No Drives/Key/Caddies *READ*
$94.99
1U Supermicro Server 10 Bay 2x Intel Xeon 3.3Ghz 8C 128GB RAM 480GB SSD 2x 10GBE
$297.00
SUPERMICRO CSE-512 AMD Opteron Processor 6128, 32GB DDR3 RAM NO HDD
$90.00