On Wed, Aug 24, 2016 at 09:35:37AM -0400, Peter Krempa wrote:
Add support for using the new approach to hotplug vcpus using device_add
during startup of qemu to allow sparse vcpu topologies.
There are a few limitations imposed by qemu on the supported
configuration:
- vcpu0 needs to be always present and not hotpluggable
- non-hotpluggable cpus need to be ordered at the beginning
- order of the vcpus needs to be unique for every single hotpluggable
entity
Qemu also doesn't really allow to query the information necessary to
start a VM with the vcpus directly on the commandline. Fortunately they
can be hotplugged during startup.
The new hotplug code uses the following approach:
- non-hotpluggable vcpus are counted and put to the -smp option
- qemu is started
- qemu is queried for the necessary information
- the configuration is checked
- the hotpluggable vcpus are hotplugged
- vcpus are started
This patch adds a lot of checking code and enables the support to
specify the individual vcpu element with qemu.
---
Notes:
v3:
- fixed qsort comparison function (added dereference of one level)
v3:
- added docs to the HTML stating qemu restrictions.
docs/formatdomain.html.in | 5 +
src/qemu/qemu_command.c | 20 ++-
src/qemu/qemu_domain.c | 76 ++++++++-
src/qemu/qemu_process.c | 178 +++++++++++++++++++++
.../qemuxml2argv-cpu-hotplug-startup.args | 20 +++
.../qemuxml2argv-cpu-hotplug-startup.xml | 29 ++++
tests/qemuxml2argvtest.c | 2 +
7 files changed, 325 insertions(+), 5 deletions(-)
create mode 100644 tests/qemuxml2argvdata/qemuxml2argv-cpu-hotplug-startup.args
create mode 100644 tests/qemuxml2argvdata/qemuxml2argv-cpu-hotplug-startup.xml
diff --git a/docs/formatdomain.html.in b/docs/formatdomain.html.in
index 062045b..8d3168a 100644
--- a/docs/formatdomain.html.in
+++ b/docs/formatdomain.html.in
@@ -580,6 +580,11 @@
Note that providing state for individual cpus may be necessary to enable
support of addressable vCPU hotplug and this feature may not be
supported by all hypervisors.
+
+ For QEMU the following conditions are required. Vcpu 0 needs to be
+ enabled and non-hotpluggable. On PPC64 along with it vcpus that are in
+ the same core need to be enabled as well. All non hotpluggable cpus
non-hotpluggable?
+ present at boot need to be grouped after vcpu 0.
<span class="since">Since 2.2.0 (QEMU only)</span>
</dd>
</dl>
diff --git a/src/qemu/qemu_command.c b/src/qemu/qemu_command.c
index 28e5a7e..c1dc390 100644
--- a/src/qemu/qemu_command.c
+++ b/src/qemu/qemu_command.c
@@ -7082,17 +7082,29 @@ qemuBuildMachineCommandLine(virCommandPtr cmd,
static int
qemuBuildSmpCommandLine(virCommandPtr cmd,
- const virDomainDef *def)
+ virDomainDefPtr def)
{
char *smp;
virBuffer buf = VIR_BUFFER_INITIALIZER;
+ unsigned int maxvcpus = virDomainDefGetVcpusMax(def);
+ unsigned int nvcpus = 0;
+ virDomainVcpuDefPtr vcpu;
+ size_t i;
+
+ /* count un-hotpluggable enabled vcpus. Hotpluggable ones will be added
non-hotpluggable?
+ * in a different way */
+ for (i = 0; i < maxvcpus; i++) {
+ vcpu = virDomainDefGetVcpu(def, i);
+ if (vcpu->online && vcpu->hotpluggable == VIR_TRISTATE_BOOL_NO)
+ nvcpus++;
+ }
virCommandAddArg(cmd, "-smp");
- virBufferAsprintf(&buf, "%u", virDomainDefGetVcpus(def));
+ virBufferAsprintf(&buf, "%u", nvcpus);
- if (virDomainDefHasVcpusOffline(def))
- virBufferAsprintf(&buf, ",maxcpus=%u", virDomainDefGetVcpusMax(def));
+ if (nvcpus != maxvcpus)
+ virBufferAsprintf(&buf, ",maxcpus=%u", maxvcpus);
/* sockets, cores, and threads are either all zero
* or all non-zero, thus checking one of them is enough */
if (def->cpu && def->cpu->sockets) {
diff --git a/src/qemu/qemu_domain.c b/src/qemu/qemu_domain.c
index aa93498..970c34a 100644
--- a/src/qemu/qemu_domain.c
+++ b/src/qemu/qemu_domain.c
@@ -2253,6 +2253,76 @@ qemuDomainRecheckInternalPaths(virDomainDefPtr def,
static int
+qemuDomainDefVcpusPostParse(virDomainDefPtr def)
+{
+ unsigned int maxvcpus = virDomainDefGetVcpusMax(def);
+ virDomainVcpuDefPtr vcpu;
+ virDomainVcpuDefPtr prevvcpu;
+ size_t i;
+ bool has_order = false;
+
+ /* vcpu 0 needs to be present, first, and non-hotpluggable */
+ vcpu = virDomainDefGetVcpu(def, 0);
+ if (!vcpu->online) {
+ virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
+ _("vcpu 0 can't be offline"));
+ return -1;
+ }
+ if (vcpu->hotpluggable == VIR_TRISTATE_BOOL_YES) {
+ virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
+ _("vcpu0 can't be hotpluggable"));
+ return -1;
+ }
+ if (vcpu->order != 0 && vcpu->order != 1) {
+ virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
+ _("vcpu0 must be enabled first"));
+ return -1;
+ }
+
+ if (vcpu->order != 0)
+ has_order = true;
+
+ prevvcpu = vcpu;
+
+ /* all online vcpus or non online vcpu need to have order set */
+ for (i = 1; i < maxvcpus; i++) {
+ vcpu = virDomainDefGetVcpu(def, i);
+
+ if (vcpu->online &&
+ (vcpu->order != 0) != has_order) {
+ virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
+ _("all vcpus must have either set or unset order"));
+ return -1;
+ }
+
+ /* few conditions for non-hotpluggable (thus online) vcpus */
+ if (vcpu->hotpluggable == VIR_TRISTATE_BOOL_NO) {
+ /* they can be ordered only at the beinning */
beginning ACK Jan
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