Comment 29 for bug 1856335

h-sieger,
that is a misunderstanding, read my comment carefully again:
"A workaround for Linux VMs is to disable CPUs (and setting their number/pinnings accordingly, e.g. every 4th (and 3rd for 3100) core is going to be 'dummy' and disabled system-wide) by e.g. echo 0 > /sys/devices/system/cpu/cpu3/online

No good workaround for Windows VMs exists, as far as I know - the best you can do is setting affinity to specific process(es) and avoid the 'dummy' CPUs, but I am not aware of any possibility to disable specific CPUs (only limiting the overall number)."

I do NOT have a fix - only a very ugly workaround for Linux guests only - I cannot fix the cache layout, but on Linux, I can get around that by adding dummy CPUs that I then disable in the guest during startup, so they are not used - effectively making sure that only the correct 6 vCPUs / 3 cores are used. On Windows, you cannot do that, AFAIK.