Re: [libvirt] [PATCH v2 04/23] qemu: Forbid config when topology based cpu count doesn't match the config

On 08/19/2016 10:38 AM, Peter Krempa wrote: > As of qemu commit: > commit a32ef3bfc12c8d0588f43f74dcc5280885bbdb30 > Author: Thomas Huth <thuth(a)redhat.com&gt; > Date: Wed Jul 22 15:59:50 2015 +0200 > > vl: Add another sanity check to smp_parse() function > > v2.4.0-952-ga32ef3b > > configuration where the maximum CPU count doesn't match the topology is > rejected. Prior to that only configurations where the topology would > contain more cpus than the maximum count would be rejected. > > Use QEMU_CAPS_QUERY_HOTPLUGGABLE_CPUS as a relevant recent enough > witness to avoid breaking old configs. > --- > > Notes: > v2: > -fixed typo in commit message > - already ACKed > > src/qemu/qemu_domain.c | 38 ++++++++++++++++++++++++++++++++------ > 1 file changed, 32 insertions(+), 6 deletions(-)

> + /* qemu as of 2.5.0 rejects SMP topologies that don't match the cpu count */ > + if (def->cpu && def->cpu->sockets) { > + topologycpus = def->cpu->sockets * def->cpu->cores * def->cpu->threads; > + if (topologycpus != virDomainDefGetVcpusMax(def)) { > + /* presence of query-hotpluggable-cpus should be a good enough witness */ > + if (virQEMUCapsGet(qemuCaps, QEMU_CAPS_QUERY_HOTPLUGGABLE_CPUS)) { > + virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s", > + _("CPU topology doesn't match maximum vcpu count")); > + goto cleanup; > + } Would it be a good idea to add a VIR_WARN or VIR_INFO (something) that will give a heads up that the configuration may prevent some future start? Especially since you went through all the math before detecting the capability...