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 IT bv
Burgemeester Mollaan 34a
5582 CK Waalre - NL
kvk 66494931

+31 (0)88 2088 188
nefos.com

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