Hi list, On a Compute Node we're seeing the following:

2025-09-12 15:10:37.052 735327 ERROR oslo_service.service Traceback (most recent call last): 2025-09-12 15:10:37.052 735327 ERROR oslo_service.service   File "/usr/lib/python3/dist-packages/nova/virt/libvirt/driver.py", line 788, in _check_cpu_compatibility 2025-09-12 15:10:37.052 735327 ERROR oslo_service.service self._compare_cpu(cpu, self._get_cpu_info(), None) 2025-09-12 15:10:37.052 735327 ERROR oslo_service.service   File "/usr/lib/python3/dist-packages/nova/virt/libvirt/driver.py", line 9029, in _compare_cpu 2025-09-12 15:10:37.052 735327 ERROR oslo_service.service raise exception.InvalidCPUInfo(reason=m % {'ret': ret, 'u': u}) 2025-09-12 15:10:37.052 735327 ERROR oslo_service.service nova.exception.InvalidCPUInfo: Unacceptable CPU info: CPU doesn't have compatibility. 2025-09-12 15:10:37.052 735327 ERROR oslo_service.service 2025-09-12 15:10:37.052 735327 ERROR oslo_service.service 0 2025-09-12 15:10:37.052 735327 ERROR oslo_service.service 2025-09-12 15:10:37.052 735327 ERROR oslo_service.service Refer to http://libvirt.org/html/libvirt-libvirt-host.html#virCPUCompareResult 2025-09-12 15:10:37.052 735327 ERROR oslo_service.service 2025-09-12 15:10:37.052 735327 ERROR oslo_service.service During handling of the above exception, another exception occurred: 2025-09-12 15:10:37.052 735327 ERROR oslo_service.service 2025-09-12 15:10:37.052 735327 ERROR oslo_service.service Traceback (most recent call last): 2025-09-12 15:10:37.052 735327 ERROR oslo_service.service   File "/usr/lib/python3/dist-packages/oslo_service/service.py", line 807, in run_service 2025-09-12 15:10:37.052 735327 ERROR oslo_service.service service.start() 2025-09-12 15:10:37.052 735327 ERROR oslo_service.service   File "/usr/lib/python3/dist-packages/nova/service.py", line 159, in start 2025-09-12 15:10:37.052 735327 ERROR oslo_service.service self.manager.init_host() 2025-09-12 15:10:37.052 735327 ERROR oslo_service.service   File "/usr/lib/python3/dist-packages/nova/compute/manager.py", line 1421, in init_host 2025-09-12 15:10:37.052 735327 ERROR oslo_service.service self.driver.init_host(host=self.host) 2025-09-12 15:10:37.052 735327 ERROR oslo_service.service   File "/usr/lib/python3/dist-packages/nova/virt/libvirt/driver.py", line 723, in init_host 2025-09-12 15:10:37.052 735327 ERROR oslo_service.service self._check_cpu_compatibility() 2025-09-12 15:10:37.052 735327 ERROR oslo_service.service   File "/usr/lib/python3/dist-packages/nova/virt/libvirt/driver.py", line 794, in _check_cpu_compatibility 2025-09-12 15:10:37.052 735327 ERROR oslo_service.service raise exception.InvalidCPUInfo(msg) 2025-09-12 15:10:37.052 735327 ERROR oslo_service.service nova.exception.InvalidCPUInfo: Configured extra flag: ibpb it not correct, or the host CPU does not support this flag. Please correct the config and try again. Unacceptable CPU info: CPU doesn't have compatibility. 2025-09-12 15:10:37.052 735327 ERROR oslo_service.service 2025-09-12 15:10:37.052 735327 ERROR oslo_service.service 0 2025-09-12 15:10:37.052 735327 ERROR oslo_service.service 2025-09-12 15:10:37.052 735327 ERROR oslo_service.service Refer to http://libvirt.org/html/libvirt-libvirt-host.html#virCPUCompareResult 2025-09-12 15:10:37.052 735327 ERROR oslo_service.service

This is very interesting, since the CPU supports the ibpb flag for sure (i.e. /proc/cpuinfo cleary lists the feature). Manually adding:

<feature policy="require" name="ibpb"/>

to the XML definition works and libvirt is happy. Is there some other name or alias for ibpb we should use? Cheers, Kees __ Kees Meijs BICT Nefos Cloud & IT <https://nefos.com/contact> Nefos IT bv Burgemeester Mollaan 34a 5582 CK Waalre - NL kvk 66494931 +31 (0)88 2088 188 <tel:+31882088188> nefos.com <https://nefos.com/contact> The information contained in this message is intended for the addressee only and may contain classified information. If you are not the addressee, please delete this message and notify the sender; you should not copy or distribute this message or disclose its contents to anyone. Any views or opinions expressed in this message are those of the individual(s) and not necessarily of the organization. No reliance may be placed on this message without written confirmation from an authorised representative of its contents. No guarantee is implied that this message or any attachment is virus free or has not been intercepted and amended. General terms and conditions ("The NLdigital Terms") apply to all our products and services.