[Qemu-devel] [PATCH v0] spapr: Error out when CPU hotplug is attempted on older pseries machines

[Bharata B Rao <bharata@linux.vnet.ibm.com>]

CPU hotplug and coldplug aren't supported prior to pseries-2.7.
query-hotpluggable-cpus and coldplug on older pseries machines are crashing
the QEMU. Fix this.

- Let query_hotpluggable_cpus return NULL for pseries < 2.7
- spapr_core_pre_plug() should fail hot/cold plug attempts for pseries < 2.7
- spapr_core_plug() should never be called for pseries < 2.7, hence use
  an assert.

Signed-off-by: Bharata B Rao <bharata@linux.vnet.ibm.com>
---
Applies on ppc-for-2.7 branch of David's tree.

 hw/ppc/spapr.c          |  5 +++++
 hw/ppc/spapr_cpu_core.c | 19 ++++++-------------
 2 files changed, 11 insertions(+), 13 deletions(-)

diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
index 7f33a1b..e3a7912 100644
--- a/hw/ppc/spapr.c
+++ b/hw/ppc/spapr.c
@@ -2368,9 +2368,14 @@ static HotpluggableCPUList *spapr_query_hotpluggable_cpus(MachineState *machine)
     int i;
     HotpluggableCPUList *head = NULL;
     sPAPRMachineState *spapr = SPAPR_MACHINE(machine);
+    sPAPRMachineClass *smc = SPAPR_MACHINE_GET_CLASS(machine);
     int spapr_max_cores = max_cpus / smp_threads;
     int smt = kvmppc_smt_threads();
 
+    if (!smc->dr_cpu_enabled) {
+        return NULL;
+    }
+
     for (i = 0; i < spapr_max_cores; i++) {
         HotpluggableCPUList *list_item = g_new0(typeof(*list_item), 1);
         HotpluggableCPU *cpu_item = g_new0(typeof(*cpu_item), 1);
diff --git a/hw/ppc/spapr_cpu_core.c b/hw/ppc/spapr_cpu_core.c
index 70b6b0b..273207c 100644
--- a/hw/ppc/spapr_cpu_core.c
+++ b/hw/ppc/spapr_cpu_core.c
@@ -162,19 +162,12 @@ void spapr_core_plug(HotplugHandler *hotplug_dev, DeviceState *dev,
     int index;
     int smt = kvmppc_smt_threads();
 
+    g_assert(smc->dr_cpu_enabled);
+
     drc = spapr_dr_connector_by_id(SPAPR_DR_CONNECTOR_TYPE_CPU, cc->core_id);
     index = cc->core_id / smt;
     spapr->cores[index] = OBJECT(dev);
 
-    if (!smc->dr_cpu_enabled) {
-        /*
-         * This is a cold plugged CPU core but the machine doesn't support
-         * DR. So skip the hotplug path ensuring that the core is brought
-         * up online with out an associated DR connector.
-         */
-        return;
-    }
-
     g_assert(drc);
 
     /*
@@ -223,13 +216,13 @@ void spapr_core_pre_plug(HotplugHandler *hotplug_dev, DeviceState *dev,
     char *base_core_type = spapr_get_cpu_core_type(machine->cpu_model);
     const char *type = object_get_typename(OBJECT(dev));
 
-    if (strcmp(base_core_type, type)) {
-        error_setg(&local_err, "CPU core type should be %s", base_core_type);
+    if (!smc->dr_cpu_enabled) {
+        error_setg(&local_err, "CPU hotplug not supported for this machine");
         goto out;
     }
 
-    if (!smc->dr_cpu_enabled && dev->hotplugged) {
-        error_setg(&local_err, "CPU hotplug not supported for this machine");
+    if (strcmp(base_core_type, type)) {
+        error_setg(&local_err, "CPU core type should be %s", base_core_type);
         goto out;
     }
 
-- 
2.7.4