Comment 1 for bug 1944484

Something like this should be safe guarding the cpu_model.

diff --git a/hooks/nova_compute_context.py b/hooks/nova_compute_context.py
index 74f8f92..2fc40c6 100644
--- a/hooks/nova_compute_context.py
+++ b/hooks/nova_compute_context.py
@@ -241,7 +241,7 @@ class NovaComputeLibvirtContext(context.OSContextGenerator):
         elif ctxt['arch'] == 's390x':
             ctxt['cpu_mode'] = 'none'

- if config('cpu-model'):
+ if config('cpu-model') and ctxt['cpu_mode'] == 'custom' and config('virt-type') in ['kvm', 'qemu']:
             ctxt['cpu_model'] = config('cpu-model')

         if config('cpu-model-extra-flags'):