Note: This bug is displayed in read-only format because
the product is no longer active in Red Hat Bugzilla.
RHEL Engineering is moving the tracking of its product development work on RHEL 6 through RHEL 9 to Red Hat Jira (issues.redhat.com). If you're a Red Hat customer, please continue to file support cases via the Red Hat customer portal. If you're not, please head to the "RHEL project" in Red Hat Jira and file new tickets here. Individual Bugzilla bugs in the statuses "NEW", "ASSIGNED", and "POST" are being migrated throughout September 2023. Bugs of Red Hat partners with an assigned Engineering Partner Manager (EPM) are migrated in late September as per pre-agreed dates. Bugs against components "kernel", "kernel-rt", and "kpatch" are only migrated if still in "NEW" or "ASSIGNED". If you cannot log in to RH Jira, please consult article #7032570. That failing, please send an e-mail to the RH Jira admins at rh-issues@redhat.com to troubleshoot your issue as a user management inquiry. The email creates a ServiceNow ticket with Red Hat. Individual Bugzilla bugs that are migrated will be moved to status "CLOSED", resolution "MIGRATED", and set with "MigratedToJIRA" in "Keywords". The link to the successor Jira issue will be found under "Links", have a little "two-footprint" icon next to it, and direct you to the "RHEL project" in Red Hat Jira (issue links are of type "https://issues.redhat.com/browse/RHEL-XXXX", where "X" is a digit). This same link will be available in a blue banner at the top of the page informing you that that bug has been migrated.
Cause: Libvirt did not recognize some CPU features as supported by QEMU because of missing translation between QEMU and libvirt CPU names.
Consequence: When starting a domain with such features explicitly disabled in CPU configuration libvirt would not ask QEMU to disable them. Depending on domain configuration the domain would either fail to start or start with an unexpected configuration.
Fix: Libvirt translates CPU feature names fetched from QEMU in case they differ to make sure no feature is wrongly considered unsupported by QEMU.
Result: All explicitly disabled CPU features known to QEMU are properly mentioned on QEMU command line and the domain is started with the requested configuration.
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.
For information on the advisory, and where to find the updated
files, follow the link below.
If the solution does not work for you, open a new bug report.
https://access.redhat.com/errata/RHSA-2020:1358
Reproduced this bug with libvirt-4.5.0-35.2.module+el8.1.0+5256+4b9ab730.x86_64. Verified this bug with libvirt-4.5.0-35.3.module+el8.1.0+5931+8897e7e1.x86_64. Version: libvirt-4.5.0-35.2.module+el8.1.0+5256+4b9ab730.x86_64 qemu-kvm-2.12.0-88.module+el8.1.0+5708+85d8e057.3.x86_64 kernel-4.18.0-147.el8.x86_64 Steps: 1. Preprare a shutdown VM with the following conf # virsh domstate test81 shut off # virsh dumpxml test81 --inactive |grep "<domain t" <domain type='qemu'> # virsh dumpxml test81 --inactive |grep "<cpu" -A29 <cpu mode='custom' match='exact' check='full'> <model fallback='forbid'>EPYC</model> <vendor>AMD</vendor> <feature policy='require' name='acpi'/> <feature policy='require' name='ss'/> <feature policy='require' name='hypervisor'/> <feature policy='require' name='erms'/> <feature policy='require' name='mpx'/> <feature policy='require' name='pcommit'/> <feature policy='require' name='clwb'/> <feature policy='require' name='pku'/> <feature policy='require' name='ospke'/> <feature policy='require' name='la57'/> <feature policy='require' name='3dnowext'/> <feature policy='require' name='3dnow'/> <feature policy='disable' name='vme'/> <feature policy='disable' name='fma'/> <feature policy='disable' name='avx'/> <feature policy='disable' name='f16c'/> <feature policy='disable' name='rdrand'/> <feature policy='disable' name='avx2'/> <feature policy='disable' name='rdseed'/> <feature policy='disable' name='sha-ni'/> <feature policy='disable' name='xsavec'/> <feature policy='disable' name='misalignsse'/> <feature policy='disable' name='3dnowprefetch'/> <feature policy='disable' name='osvw'/> <feature policy='disable' name='topoext'/> <feature policy='disable' name='fxsr_opt'/> </cpu> 2. Start VM and check the log # virsh start test81 error: Failed to start domain test81 error: operation failed: guest CPU doesn't match specification: missing features: fxsr_opt # tail -f /var/log/libvirt/qemu/test81.log 2020-03-09T02:23:15.501270Z qemu-kvm: warning: TCG doesn't support requested feature: CPUID.80000001H:EDX.fxsr-opt [bit 25] 2020-03-09T02:23:15.501943Z qemu-kvm: warning: TCG doesn't support requested feature: CPUID.80000001H:EDX.fxsr-opt [bit 25] 3. Update libvirt and restart libvirtd # yum update libvirt* -y # systemctl restart libvirtd # rpm -qa libvirt libvirt-4.5.0-35.3.module+el8.1.0+5931+8897e7e1.x86_64 4. Start the VM again and check the qemu cmd line/active dumpxml # virsh start test81 Domain test81 started # ps -ef |grep test81 -cpu EPYC,acpi=on,ss=on,hypervisor=on,erms=on,mpx=on,pcommit=on,clwb=on,pku=on,ospke=on,la57=on,3dnowext=on,3dnow=on,vme=off,fma=off,avx=off,f16c=off,rdrand=off,avx2=off,rdseed=off,sha-ni=off,xsavec=off,misalignsse=off,3dnowprefetch=off,osvw=off,topoext=off,fxsr-opt=off # virsh dumpxml test81 | grep "<cpu" -A30 <cpu mode='custom' match='exact' check='full'> <model fallback='forbid'>EPYC</model> <vendor>AMD</vendor> <feature policy='require' name='acpi'/> <feature policy='require' name='ss'/> <feature policy='require' name='hypervisor'/> <feature policy='require' name='erms'/> <feature policy='require' name='mpx'/> <feature policy='require' name='pcommit'/> <feature policy='require' name='clwb'/> <feature policy='require' name='pku'/> <feature policy='require' name='ospke'/> <feature policy='require' name='la57'/> <feature policy='require' name='3dnowext'/> <feature policy='require' name='3dnow'/> <feature policy='disable' name='vme'/> <feature policy='disable' name='fma'/> <feature policy='disable' name='avx'/> <feature policy='disable' name='f16c'/> <feature policy='disable' name='rdrand'/> <feature policy='disable' name='avx2'/> <feature policy='disable' name='rdseed'/> <feature policy='disable' name='sha-ni'/> <feature policy='disable' name='xsavec'/> <feature policy='disable' name='misalignsse'/> <feature policy='disable' name='3dnowprefetch'/> <feature policy='disable' name='osvw'/> <feature policy='disable' name='topoext'/> <feature policy='disable' name='fxsr_opt'/> </cpu>