[Qemu-devel] [PULL 15/18] spapr: CPU hot unplug support

[David Gibson <david@gibson.dropbear.id.au>]

From: Bharata B Rao <bharata@linux.vnet.ibm.com>

Remove the CPU core device by removing the underlying CPU thread devices.
Hot removal of CPU for sPAPR guests is achieved by sending the hot unplug
notification to the guest. Release the vCPU object after CPU hot unplug so
that vCPU fd can be parked and reused.

Signed-off-by: Bharata B Rao <bharata@linux.vnet.ibm.com>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
---
 hw/ppc/spapr.c                  |  8 ++++++
 hw/ppc/spapr_cpu_core.c         | 59 +++++++++++++++++++++++++++++++++++++++++
 include/hw/ppc/spapr_cpu_core.h |  2 ++
 3 files changed, 69 insertions(+)

diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
index c444a86..1dcb9f6 100644
--- a/hw/ppc/spapr.c
+++ b/hw/ppc/spapr.c
@@ -2313,8 +2313,16 @@ 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());
+
     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) {
+            error_setg(errp, "CPU hot unplug not supported on this machine");
+            return;
+        }
+        spapr_core_unplug(hotplug_dev, dev, errp);
     }
 }
 
diff --git a/hw/ppc/spapr_cpu_core.c b/hw/ppc/spapr_cpu_core.c
index d5fa4e6..3a5da09 100644
--- a/hw/ppc/spapr_cpu_core.c
+++ b/hw/ppc/spapr_cpu_core.c
@@ -38,6 +38,14 @@ static void spapr_cpu_reset(void *opaque)
                                 &error_fatal);
 }
 
+static void spapr_cpu_destroy(PowerPCCPU *cpu)
+{
+    sPAPRMachineState *spapr = SPAPR_MACHINE(qdev_get_machine());
+
+    xics_cpu_destroy(spapr->icp, cpu);
+    qemu_unregister_reset(spapr_cpu_reset, cpu);
+}
+
 void spapr_cpu_init(sPAPRMachineState *spapr, PowerPCCPU *cpu, Error **errp)
 {
     CPUPPCState *env = &cpu->env;
@@ -88,6 +96,57 @@ char *spapr_get_cpu_core_type(const char *model)
     return core_type;
 }
 
+static void spapr_core_release(DeviceState *dev, void *opaque)
+{
+    sPAPRCPUCore *sc = SPAPR_CPU_CORE(OBJECT(dev));
+    const char *typename = object_class_get_name(sc->cpu_class);
+    size_t size = object_type_get_instance_size(typename);
+    sPAPRMachineState *spapr = SPAPR_MACHINE(qdev_get_machine());
+    sPAPRCPUCore *core = SPAPR_CPU_CORE(OBJECT(dev));
+    CPUCore *cc = CPU_CORE(dev);
+    int smt = kvmppc_smt_threads();
+    int i;
+
+    for (i = 0; i < cc->nr_threads; i++) {
+        void *obj = sc->threads + i * size;
+        DeviceState *dev = DEVICE(obj);
+        CPUState *cs = CPU(dev);
+        PowerPCCPU *cpu = POWERPC_CPU(cs);
+
+        spapr_cpu_destroy(cpu);
+        cpu_remove_sync(cs);
+        object_unparent(obj);
+    }
+
+    spapr->cores[cc->core_id / smt] = NULL;
+
+    g_free(core->threads);
+    object_unparent(OBJECT(dev));
+}
+
+void spapr_core_unplug(HotplugHandler *hotplug_dev, DeviceState *dev,
+                       Error **errp)
+{
+    sPAPRCPUCore *core = SPAPR_CPU_CORE(OBJECT(dev));
+    PowerPCCPU *cpu = POWERPC_CPU(core->threads);
+    int id = ppc_get_vcpu_dt_id(cpu);
+    sPAPRDRConnector *drc =
+        spapr_dr_connector_by_id(SPAPR_DR_CONNECTOR_TYPE_CPU, id);
+    sPAPRDRConnectorClass *drck;
+    Error *local_err = NULL;
+
+    g_assert(drc);
+
+    drck = SPAPR_DR_CONNECTOR_GET_CLASS(drc);
+    drck->detach(drc, dev, spapr_core_release, NULL, &local_err);
+    if (local_err) {
+        error_propagate(errp, local_err);
+        return;
+    }
+
+    spapr_hotplug_req_remove_by_index(drc);
+}
+
 void spapr_core_plug(HotplugHandler *hotplug_dev, DeviceState *dev,
                      Error **errp)
 {
diff --git a/include/hw/ppc/spapr_cpu_core.h b/include/hw/ppc/spapr_cpu_core.h
index 7cb0515..1c9b319 100644
--- a/include/hw/ppc/spapr_cpu_core.h
+++ b/include/hw/ppc/spapr_cpu_core.h
@@ -31,4 +31,6 @@ void spapr_core_pre_plug(HotplugHandler *hotplug_dev, DeviceState *dev,
 char *spapr_get_cpu_core_type(const char *model);
 void spapr_core_plug(HotplugHandler *hotplug_dev, DeviceState *dev,
                      Error **errp);
+void spapr_core_unplug(HotplugHandler *hotplug_dev, DeviceState *dev,
+                       Error **errp);
 #endif
-- 
2.5.5