spapr: Correctly set query_hotpluggable_cpus hook based on machine version

Prior to c8721d3 "spapr: Error out when CPU hotplug is attempted on older
pseries machines", attempting to use query-hotpluggable-cpus on pseries-2.6
and earlier machine types would SEGV.

That change fixed that, but due to some unexpected interactions in init
order and a brown-paper-bag worthy failure to test, it accidentally
disabled query-hotpluggable-cpus for all pseries machine types, including
the current one which should allow it.

In fact, query_hotpluggable_cpus needs to be non-NULL when and only when
the dr_cpu_enabled flag in sPAPRMachineClass is set, which makes
dr_cpu_enabled itself redundant.

This patch removes dr_cpu_enabled, instead directly setting
query_hotpluggable_cpus from the machine class_init functions, and using
that to determine the availability of CPU hotplug when necessary.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>

hw/ppc/spapr.c

@@ -938,6 +938,7 @@ static void spapr_finalize_fdt(sPAPRMachineState *spapr,
                                hwaddr rtas_size)
 {
     MachineState *machine = MACHINE(qdev_get_machine());
+    MachineClass *mc = MACHINE_GET_CLASS(machine);
     sPAPRMachineClass *smc = SPAPR_MACHINE_GET_CLASS(machine);
     const char *boot_device = machine->boot_order;
     int ret, i;
@@ -1020,7 +1021,7 @@ static void spapr_finalize_fdt(sPAPRMachineState *spapr,
         _FDT(spapr_drc_populate_dt(fdt, 0, NULL, SPAPR_DR_CONNECTOR_TYPE_LMB));
     }
 
-    if (smc->dr_cpu_enabled) {
+    if (mc->query_hotpluggable_cpus) {
         int offset = fdt_path_offset(fdt, "/cpus");
         ret = spapr_drc_populate_dt(fdt, offset, NULL,
                                     SPAPR_DR_CONNECTOR_TYPE_CPU);
@@ -1712,6 +1713,7 @@ static void spapr_validate_node_memory(MachineState *machine, Error **errp)
 static void ppc_spapr_init(MachineState *machine)
 {
     sPAPRMachineState *spapr = SPAPR_MACHINE(machine);
+    MachineClass *mc = MACHINE_GET_CLASS(machine);
     sPAPRMachineClass *smc = SPAPR_MACHINE_GET_CLASS(machine);
     const char *kernel_filename = machine->kernel_filename;
     const char *kernel_cmdline = machine->kernel_cmdline;
@@ -1733,7 +1735,7 @@ static void ppc_spapr_init(MachineState *machine)
     int spapr_cores = smp_cpus / smp_threads;
     int spapr_max_cores = max_cpus / smp_threads;
 
-    if (smc->dr_cpu_enabled) {
+    if (mc->query_hotpluggable_cpus) {
         if (smp_cpus % smp_threads) {
             error_report("smp_cpus (%u) must be multiple of threads (%u)",
                          smp_cpus, smp_threads);
@@ -1810,7 +1812,7 @@ static void ppc_spapr_init(MachineState *machine)
         machine->cpu_model = kvm_enabled() ? "host" : "POWER7";
     }
 
-    if (smc->dr_cpu_enabled) {
+    if (mc->query_hotpluggable_cpus) {
         char *type = spapr_get_cpu_core_type(machine->cpu_model);
 
         spapr->cores = g_new0(Object *, spapr_max_cores);
@@ -2333,12 +2335,12 @@ static void spapr_machine_device_plug(HotplugHandler *hotplug_dev,
 static void spapr_machine_device_unplug(HotplugHandler *hotplug_dev,
                                       DeviceState *dev, Error **errp)
 {
-    sPAPRMachineClass *smc = SPAPR_MACHINE_GET_CLASS(qdev_get_machine());
+    MachineClass *mc = MACHINE_GET_CLASS(qdev_get_machine());
 
     if (object_dynamic_cast(OBJECT(dev), TYPE_PC_DIMM)) {
         error_setg(errp, "Memory hot unplug not supported by sPAPR");
     } else if (object_dynamic_cast(OBJECT(dev), TYPE_SPAPR_CPU_CORE)) {
-        if (!smc->dr_cpu_enabled) {
+        if (!mc->query_hotpluggable_cpus) {
             error_setg(errp, "CPU hot unplug not supported on this machine");
             return;
         }
@@ -2376,11 +2378,8 @@ 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;
 
-    g_assert(smc->dr_cpu_enabled);
-
     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);
@@ -2435,12 +2434,9 @@ static void spapr_machine_class_init(ObjectClass *oc, void *data)
     hc->plug = spapr_machine_device_plug;
     hc->unplug = spapr_machine_device_unplug;
     mc->cpu_index_to_socket_id = spapr_cpu_index_to_socket_id;
-    if (smc->dr_cpu_enabled) {
-        mc->query_hotpluggable_cpus = spapr_query_hotpluggable_cpus;
-    }
 
     smc->dr_lmb_enabled = true;
-    smc->dr_cpu_enabled = true;
+    mc->query_hotpluggable_cpus = spapr_query_hotpluggable_cpus;
     fwc->get_dev_path = spapr_get_fw_dev_path;
     nc->nmi_monitor_handler = spapr_nmi;
 }
@@ -2521,10 +2517,8 @@ static void spapr_machine_2_6_instance_options(MachineState *machine)
 
 static void spapr_machine_2_6_class_options(MachineClass *mc)
 {
-    sPAPRMachineClass *smc = SPAPR_MACHINE_CLASS(mc);
-
     spapr_machine_2_7_class_options(mc);
-    smc->dr_cpu_enabled = false;
+    mc->query_hotpluggable_cpus = NULL;
     SET_MACHINE_COMPAT(mc, SPAPR_COMPAT_2_6);
 }
 

hw/ppc/spapr_cpu_core.c

@@ -153,7 +153,6 @@ void spapr_core_unplug(HotplugHandler *hotplug_dev, DeviceState *dev,
 void spapr_core_plug(HotplugHandler *hotplug_dev, DeviceState *dev,
                      Error **errp)
 {
-    sPAPRMachineClass *smc = SPAPR_MACHINE_GET_CLASS(OBJECT(hotplug_dev));
     sPAPRMachineState *spapr = SPAPR_MACHINE(OBJECT(hotplug_dev));
     sPAPRCPUCore *core = SPAPR_CPU_CORE(OBJECT(dev));
     CPUCore *cc = CPU_CORE(dev);
@@ -166,8 +165,6 @@ void spapr_core_plug(HotplugHandler *hotplug_dev, DeviceState *dev,
     int index = cc->core_id / smp_threads;
     int smt = kvmppc_smt_threads();
 
-    g_assert(smc->dr_cpu_enabled);
-
     drc = spapr_dr_connector_by_id(SPAPR_DR_CONNECTOR_TYPE_CPU, index * smt);
     spapr->cores[index] = OBJECT(dev);
 
@@ -209,7 +206,7 @@ void spapr_core_pre_plug(HotplugHandler *hotplug_dev, DeviceState *dev,
                          Error **errp)
 {
     MachineState *machine = MACHINE(OBJECT(hotplug_dev));
-    sPAPRMachineClass *smc = SPAPR_MACHINE_GET_CLASS(OBJECT(hotplug_dev));
+    MachineClass *mc = MACHINE_GET_CLASS(hotplug_dev);
     sPAPRMachineState *spapr = SPAPR_MACHINE(OBJECT(hotplug_dev));
     int spapr_max_cores = max_cpus / smp_threads;
     int index;
@@ -218,7 +215,7 @@ 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 (!smc->dr_cpu_enabled) {
+    if (!mc->query_hotpluggable_cpus) {
         error_setg(&local_err, "CPU hotplug not supported for this machine");
         goto out;
     }

include/hw/ppc/spapr.h

@@ -38,7 +38,6 @@ struct sPAPRMachineClass {
 
     /*< public >*/
     bool dr_lmb_enabled;       /* enable dynamic-reconfig/hotplug of LMBs */
-    bool dr_cpu_enabled;       /* enable dynamic-reconfig/hotplug of CPUs */
     bool use_ohci_by_default;  /* use USB-OHCI instead of XHCI */
 };