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qemu: Enforce vCPU hotplug granularity constraints

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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@redhat.com>
This commit is contained in:
Andrea Bolognani 2017-12-14 15:54:59 +01:00
parent 54acfac4a5
commit a38aa340fe
3 changed files with 62 additions and 0 deletions
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41
src/qemu/qemu_domain.c
View File

@ -3289,6 +3289,36 @@ qemuDomainDefValidateVideo(const virDomainDef *def)
}
/**
* qemuDomainDefGetVcpuHotplugGranularity:
* @def: domain definition
*
* With QEMU 2.7 and newer, vCPUs can only be hotplugged in groups that
* respect the guest's hotplug granularity; because of that, QEMU will
* not allow guests to start unless the initial number of vCPUs is a
* multiple of the hotplug granularity.
*
* Returns the vCPU hotplug granularity.
*/
static unsigned int
qemuDomainDefGetVcpuHotplugGranularity(const virDomainDef *def)
{
/* If the guest CPU topology has not been configured, assume we
* can hotplug vCPUs one at a time */
if (!def->cpu || def->cpu->sockets == 0)
return 1;
/* For pSeries guests, hotplug can only be performed one core
* at a time, so the vCPU hotplug granularity is the number
* of threads per core */
if (qemuDomainIsPSeries(def))
return def->cpu->threads;
/* In all other cases, we can hotplug vCPUs one at a time */
return 1;
}
#define QEMU_MAX_VCPUS_WITHOUT_EIM 255
@ -3363,6 +3393,7 @@ qemuDomainDefValidate(const virDomainDef *def,
* CPU topology. Verify known constraints are respected */
if (virQEMUCapsGet(qemuCaps, QEMU_CAPS_QUERY_HOTPLUGGABLE_CPUS)) {
unsigned int topologycpus;
unsigned int granularity;
/* Starting from QEMU 2.5, max vCPU count and overall vCPU topology
* must agree. We only actually enforce this with QEMU 2.7+, due
@ -3373,6 +3404,16 @@ qemuDomainDefValidate(const virDomainDef *def,
_("CPU topology doesn't match maximum vcpu count"));
goto cleanup;
}
/* vCPU hotplug granularity must be respected */
granularity = qemuDomainDefGetVcpuHotplugGranularity(def);
if ((virDomainDefGetVcpus(def) % granularity) != 0) {
virReportError(VIR_ERR_CONFIG_UNSUPPORTED,
_("vCPUs count must be a multiple of the vCPU "
"hotplug granularity (%u)"),
granularity);
goto cleanup;
}
}
if (ARCH_IS_X86(def->os.arch) &&

18
tests/qemuxml2argvdata/cpu-hotplug-granularity.xml Normal file
View File

@ -0,0 +1,18 @@
<domain type='qemu'>
<name>guest</name>
<uuid>1ccfd97d-5eb4-478a-bbe6-88d254c16db7</uuid>
<memory unit='KiB'>524288</memory>
<vcpu placement='static' current='2'>8</vcpu>
<os>
<type arch='ppc64' machine='pseries'>hvm</type>
</os>
<cpu>
<topology sockets='1' cores='2' threads='4'/>
</cpu>
<devices>
<emulator>/usr/bin/qemu-system-ppc64</emulator>
<controller type='pci' model='pci-root'/>
<controller type='usb' model='none'/>
<memballoon model='none'/>
</devices>
</domain>

3
tests/qemuxml2argvtest.c
View File

@ -2900,6 +2900,9 @@ mymain(void)
QEMU_CAPS_DEVICE_INTEL_IOMMU);
DO_TEST("cpu-hotplug-startup", QEMU_CAPS_QUERY_HOTPLUGGABLE_CPUS);
DO_TEST_PARSE_ERROR("cpu-hotplug-granularity",
QEMU_CAPS_QUERY_HOTPLUGGABLE_CPUS);
DO_TEST("virtio-options", QEMU_CAPS_VIRTIO_SCSI, QEMU_CAPS_VIRTIO_KEYBOARD,
QEMU_CAPS_VIRTIO_MOUSE, QEMU_CAPS_VIRTIO_TABLET,
QEMU_CAPS_VIRTIO_INPUT_HOST,