Re: [libvirt] [PATCH 2/2] qemu: Enforce vCPU hotplug granularity constraints

QEMU 2.7 and newer don't allow guests to start unless the initial vCPUs count is a multiple of the vCPU hotplug granularity, so validate it and report an error if needed. Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1283700 Signed-off-by: Andrea Bolognani <abologna(a)redhat.com&gt; --- src/qemu/qemu_domain.c | 41 ++++++++++++++++++++++ tests/qemuxml2argvdata/cpu-hotplug-granularity.xml | 18 ++++++++++ tests/qemuxml2argvtest.c | 3 ++ 3 files changed, 62 insertions(+) create mode 100644 tests/qemuxml2argvdata/cpu-hotplug-granularity.xml diff --git a/src/qemu/qemu_domain.c b/src/qemu/qemu_domain.c index e93333669..632f330f7 100644 --- a/src/qemu/qemu_domain.c +++ b/src/qemu/qemu_domain.c @@ -3289,6 +3289,36 @@ qemuDomainDefValidateVideo(const virDomainDef *def) } +/** + * qemuDomainDefGetVcpuHotplugGranularity: + * @def: domain definition + * @granularity: return location for vCPU hotplug granularity + * + * With QEMU 2.7 and newer, vCPUs can only be hotplugged @granularity at + * a time; because of that, QEMU will not allow guests to start unless the + * initial number of vCPUs is a multiple of @granularity. + * + * Returns 0 on success, 1 if topology is not configured and -1 on error. + */ +static int +qemuDomainDefGetVcpuHotplugGranularity(const virDomainDef *def, + unsigned int *granularity) +{ + if (!granularity) + return -1;

+ + if (!def->cpu || def->cpu->sockets == 0) + return 1;

+ + if (qemuDomainIsPSeries(def)) + *granularity = def->cpu->threads; + else + *granularity = 1;

+ + return 0; +} + +