Comment 5 for bug 1868692

The libvirt type doesn't add vmx=on (as expected since it defines the existing features).

Test:
- no type - qemu64 type withotu vmx=on, no nesting as-is
- qemu64 type - qemu64 type withotu vmx=on, no nesting as-is
- qemu64 with vmx - nested working
- kvm64 type - kvm64 type withotu vmx=on, no nesting as-is
- kvm64 type with vmx - nested working

So with the fixes in qemu we can:
- again enable VMX on this cpu type
- nesting works (not running into the crashes mentioned further above)

It does not yet make nesting available if you don't do anything.
Since overall this change makes things (e.g. exposed guest features) safer lets add a comment to the release notes - might be a good chance to mention host-model and named CPU types anyway, but otherwise keep it at that level.