KVM is making QEMU shoddy
QEmu is one of the best ways to run old operating systems for digital preservation but companies obsessed with "current" Linux or virtualization are messing up the codebase a little.
So little work is done for QEmu for older OSes. For example until recently QEmu had an issue on DOS with reading from the keyboard when DJGPP's DPMI manager is loaded. If we are not correctly reading from virtual hardware at this point, adding layers upon layers is going to start making it pretty flaky.
Likewise trying to boot i.e older UNIX like Solaris 9 is pretty awkward. So I can't say QEmu is exactly keeping to the x86 spec.
Yes its hard but I am surprised less people are interested in keeping legacy history working.
