Comment 17 for bug 1825195

Some details from testing that make it even less severe ...

Note: since this was never in any Host defined any required setting would have triggered a pre-check like:
  error: the CPU is incompatible with host CPU: Host CPU does not provide required features: ospke

But if set to optional:
        <cpu match="exact">
                <model>core2duo</model>
                <feature policy='optional' name='osxsave'/>
                <feature policy='optional' name='ospke'/>
        </cpu>

Then you'd hit:
error: Failed to start domain disco-osxsave
error: internal error: process exited while connecting to monitor: 2019-04-25T12:12:01.698646Z qemu-system-x86_64: can't apply global core2duo-x86_64-cpu.osxsave=off: Property '.osxsave' not found

Commandline:
 -cpu core2duo,osxsave=off,ospke=off

With the fix in place the above becomes:
  -cpu core2duo
and works again.