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Description of problem: The output of the command $ virsh cpu-models ppc64 POWERPC_e6500 POWERPC_e5500 power8 power8e power7+ power7 power6 POWER8_v1.0 POWER7+_v2.1 POWER7_v2.3 POWER7_v2.1 POWER7 includes some values, eg. POWER7_v2.1, that are not recognized by QEMU, and others, like power8e, that don't even look like proper CPU models. Moreover, even the values that *do* work are way too specific. Due to the way KVM works on POWER, you can only run a guest if its CPU model matches the host CPU model exactly; to make the situation manageable, more generic CPU models, eg. POWER8, have been introduced in QEMU and the recommended configuration is to use those instead of eg. the overspecific POWER8_v1.0. So libvirt should only advertise CPU models that can actually be used in the guest configuration, and should make sure that compatibility is reported correctly, eg. POWER7 guest can run on all POWER7* hosts but not on a POWER8* host. Version-Release number of selected component (if applicable): libvirt-daemon-1.2.17-3.el7.ppc64le How reproducible: Always. Steps to Reproduce: 1. Configure a guest to use the power8e CPU model 2. Start the guest Actual results: error: Failed to start domain test error: internal error: process exited while connecting to monitor: Unable to find PowerPC CPU definition Expected results: libvirt only advertises actual CPU models and handles compatibility between the guest and the host appropriately. Additional info: None.
This has been fixed upstream by the following commits: commit 96b2c7459cb689a27996c2d69131e245940bc533 Author: Andrea Bolognani <abologna@redhat.com> Date: Fri Aug 7 17:39:10 2015 +0200 cpu: CPU model names have to match on ppc64 Limitations of the POWER architecture mean that you can't run eg. a POWER7 guest on a POWER8 host when using KVM. This applies to all guests, not just those using VIR_CPU_MATCH_STRICT in the CPU definition; in fact, exact and strict CPU matching are basically the same on ppc64. This means, of course, that hosts using different CPUs have to be considered incompatible as well. Change ppc64Compute(), called by cpuGuestData(), to reflect this fact and update test cases accordingly. Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1250977 commit d87359af5eb5b21848da1906f8e34f107bbea151 Author: Andrea Bolognani <abologna@redhat.com> Date: Fri Aug 7 17:39:15 2015 +0200 cpu: Simplify ppc64 part of CPU map XML Use multiple PVRs per CPU model to reduce the number of models we need to keep track of. Remove specific CPU models (eg. POWER7+_v2.1): the corresponding generic CPU model (eg. POWER7) should be used instead to ensure the guest can be booted on any compatible host. Get rid of all the entries that did not match any of the CPU models supported by QEMU, like power8 and power8e. Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1250977 Complete series: https://www.redhat.com/archives/libvir-list/2015-August/msg00288.html
Andrea, Just briefly test using the scratch package on host POWER8E: libvirt-1.2.17-4.el7+abologna+bz1250977.ppc64le Something need confirmation from you. # virsh cpu-models ppc64le POWERPC_e6500 POWERPC_e5500 POWER8 POWER7 POWER6 Using configuration below: <cpu><model>POWER8</model></cpu> can work <cpu><model>POWER7</model></cpu> can print error message as expected. But a guest can start successfully using below two cpu configurations too. <cpu mode='host-model'> <model fallback='forbid'>power8</model> </cpu> qemu ... -cpu host,compat=power8 or <cpu mode='host-model'> <model fallback='allow'>power7</model> </cpu> qemu ... -cpu host,compat=power7 Question : 'power7' and 'power8' did work before. But as now they are not listed in virsh cpu-models ppc64 any more, it is a little inconsistent, right? What is your opinion?
The thing about CPU models 'power7' and 'power8' is that they are not actually CPU models: they are compatibility modes, and can only be used inside <cpu mode='host-model'/> Using the <model> tag to specify compatibility was IMHO a bad choice, as it mixes the two concepts; adding a new <compat> tag instead would have been much better. However, that's how it's been implemented and we can't really change it now. Compatibility modes will probably be advertised by libvirt at some point, but not among actual CPU models. Hopefully this explanation clears things up. It not, feel free to ask more questions :)
Test with below packages: libvirt-1.2.17-5.el7.ppc64le qemu-kvm-rhev-2.3.0-17.el7.ppc64le kernel-3.10.0-302.el7.ppc64le Below tests are done. 1. Check cpu-models output is updated with supported cpu models. # virsh cpu-models ppc64 POWERPC_e6500 POWERPC_e5500 POWER8 POWER7 POWER6 2.Check model 'POWER8' can be supported for the guest. Guest can start successfully. Qemu command line includes below option: '-cpu POWER8' <cpu><model>POWER8</model></cpu> or <cpu mode='custom' match='exact'> <model fallback='allow'>POWER8</model> </cpu> ALso test match='strict', 'minimum', the guest can start. 3.Check POWER7 guest can not run on a POWER8(POWER8E) host when using KVM Edit XML like below, start the guest. <cpu mode='custom' match='exact'> <model fallback='allow'>POWER7</model> </cpu> # virsh start q2 error: Failed to start domain q2 error: unsupported configuration: guest and host CPU are not compatible: host CPU model does not match required CPU model POWER7 Try match='strict', 'minimum', and the error message should be same. 4. Test compatibility mode. Edit the guest XML like below and start the guest. <cpu mode='host-model'> <model fallback='forbid'>power8</model> </cpu> The guest can be started successfully. When power8, '-cpu host,compat=power8' should be in qemu command line. When power7, '-cpu host,compat=power7' should be in qemu command line. Change 'power8' to 'power7' to test, the result is same as above. 5.Check below configurations should always work like before. The guest should be able to start successfully. Check qemu process, ' -cpu host' should be in qemu command line. <cpu mode='host-model'> </cpu> or <cpu mode='host-passthrough'> </cpu> 6. Check # virsh capabilities has new model displayed. '<model>POWER8</model>' is displayed instead of '<model>power8e</model>' # virsh capabilities <capabilities> <host> <uuid>113bc7e1-c986-4f34-acc4-01dcfdce8678</uuid> <cpu> <arch>ppc64le</arch> <model>POWER8</model> <vendor>IBM</vendor> ... </capabilities> All above tests are passed.
Andrea, The tests in comment 7 are done. Do you think it is enough? Welcome your suggestions. Thanks.
Due to no new comments, mark it verified.
The tests listed in Comment 7 seem to cover all of the correct configurations. If you want to be more thorough, you could also check that using invalid model names or compatibility modes, eg. <cpu mode='custom'> <model>POWER42</model> </cpu> or <cpu mode='host-model'> <model>power42</model> </cpu> prevents the guest from starting with an appropriate error message.
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://rhn.redhat.com/errata/RHBA-2015-2202.html