Finally I'm able to test on a Threadripper myself now.

Note: In regard to the commit that Babu identified - I'm on kernel 5.10.0-1020-oem so that patch would be applied already. I need to find an older kernel to retry with that as well

(on that new kernel) I did a full Win10 install and it worked fine for me.

In regard to CPU types (for comparison) I got

qemu 1:4.2-3ubuntu6.15 / libvirt 6.0.0-0ubuntu8.8:
    <mode name='host-model' supported='yes'>
      <model fallback='forbid'>EPYC-Rome</model>
      <vendor>AMD</vendor>
      <feature policy='require' name='x2apic'/>
      <feature policy='require' name='tsc-deadline'/>
      <feature policy='require' name='hypervisor'/>
      <feature policy='require' name='tsc_adjust'/>
      <feature policy='require' name='stibp'/>
      <feature policy='require' name='arch-capabilities'/>
      <feature policy='require' name='ssbd'/>
      <feature policy='require' name='xsaves'/>
      <feature policy='require' name='cmp_legacy'/>
      <feature policy='require' name='invtsc'/>
      <feature policy='require' name='amd-ssbd'/>
      <feature policy='require' name='virt-ssbd'/>
      <feature policy='require' name='rdctl-no'/>
      <feature policy='require' name='skip-l1dfl-vmentry'/>
      <feature policy='require' name='mds-no'/>
      <feature policy='require' name='pschange-mc-no'/>
    </mode>

With a more recent qemu/libvirt it isn't much different for this chip (there recently were some Milan changes, but those seem not to matter for this chip).

qemu  1:5.2+dfsg-9ubuntu1 / libvirt 7.0.0-2ubuntu1

    <mode name='host-model' supported='yes'>
      <model fallback='forbid'>EPYC-Rome</model>
      <vendor>AMD</vendor>
      <feature policy='require' name='x2apic'/>
      <feature policy='require' name='tsc-deadline'/>
      <feature policy='require' name='hypervisor'/>
      <feature policy='require' name='tsc_adjust'/>
      <feature policy='require' name='stibp'/>
      <feature policy='require' name='arch-capabilities'/>
      <feature policy='require' name='ssbd'/>
      <feature policy='require' name='xsaves'/>
      <feature policy='require' name='cmp_legacy'/>
      <feature policy='require' name='invtsc'/>
      <feature policy='require' name='amd-ssbd'/>
      <feature policy='require' name='virt-ssbd'/>
      <feature policy='require' name='rdctl-no'/>
      <feature policy='require' name='skip-l1dfl-vmentry'/>
      <feature policy='require' name='mds-no'/>
      <feature policy='require' name='pschange-mc-no'/>
    </mode>


I wasn't able to crash this setup with an old (18.04) nor a new 21.04) Ubuntu guest.
Installing Win10 worked fine for a while and didn't break as reported. But the setup I have goes through triple ssh-tunnels and around the globe - that slows things down a lot :-/
This is how far I've got:
1. start up the install
2. select no license key -> custom install -> it started copying files
3. it goes into the first reboot

After this the latency kills me and virt-manager starts to abort the installation.
So far I did not hit (https://launchpadlibrarian.net/529734412/security.png) as reported by David.
@David - did this already pass the critical step for you, how early or late in the install did you hit the issues.


As I said I'll probably need to find an older kernel anyway (to be before the commit that Babu referenced)