Modified Minix3 can run under kvm on linux on Intel-VT and AMD-SVM
If you try to run minix3 unmodified under kvm or xen then it hangs

Here is the trick,

1. Install minix using -no-kvm option for qemu.
2. Go to /usr/src/boot/
3. In boothead.s file comment out following lines by putting ! ,
line 744: ! hlt
line 643: ! hlt

4. Execute following command in the same directory,
make install

5. Goto /usr/src/tools and execute following command,
./mkboot bootable

6. Done, Now shutdown minix and start qemu without -no-kvm option.

Basically we need to modify minix boot monitor code by
commenting out "hlt" instruction in it and reinstall the new boot

Performance is very good under kvm, since there is no emulation.