Comment 33 for bug 1921754

this does seem to affect ubuntu 18.04 (bionic beaver) as well, meaning it's not possible to host guest vms with the IBRS Security Flag:

qemu-system-x86_64 -cpu ? | grep EPYC-Rome

is empty

dpkg -l qemu-system
Desired=Unknown/Install/Remove/Purge/Hold
| Status=Not/Inst/Conf-files/Unpacked/halF-conf/Half-inst/trig-aWait/Trig-pend
|/ Err?=(none)/Reinst-required (Status,Err: uppercase=bad)
||/ Name Version Architecture Description
+++-=====================================================-===============================-===============================-===============================================================================================================
ii qemu-system 1:4.0+dfsg-0ubuntu9.8