[Qemu-devel] [for-2.7 PATCH v3 12/15] spapr: CPU hot unplug support

[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>
---
 hw/ppc/spapr.c                  | 16 ++++++++
 hw/ppc/spapr_cpu_core.c         | 81 +++++++++++++++++++++++++++++++++++++++++
 include/hw/ppc/spapr.h          |  1 +
 include/hw/ppc/spapr_cpu_core.h | 11 ++++++
 4 files changed, 109 insertions(+)

diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
index 8c3100d..a8cd74d 100644
--- a/hw/ppc/spapr.c
+++ b/hw/ppc/spapr.c
@@ -2342,11 +2342,27 @@ static void spapr_machine_device_plug(HotplugHandler *hotplug_dev,
     }
 }
 
+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);
+}
+
 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 ed36beb..0b62456 100644
--- a/hw/ppc/spapr_cpu_core.c
+++ b/hw/ppc/spapr_cpu_core.c
@@ -28,6 +28,87 @@ char *spapr_get_cpu_core_type(const char *model)
     return g_strdup(core_type);
 }
 
+static void spapr_cpu_core_cleanup(struct sPAPRCPUUnplugList *unplug_list)
+{
+    sPAPRCPUUnplug *unplug, *next;
+    Object *cpu;
+
+    QLIST_FOREACH_SAFE(unplug, unplug_list, node, next) {
+        cpu = unplug->cpu;
+        object_unparent(cpu);
+        QLIST_REMOVE(unplug, node);
+        g_free(unplug);
+    }
+}
+
+static void spapr_add_cpu_to_unplug_list(Object *cpu,
+                                         struct sPAPRCPUUnplugList *unplug_list)
+{
+    sPAPRCPUUnplug *unplug = g_malloc(sizeof(*unplug));
+
+    unplug->cpu = cpu;
+    QLIST_INSERT_HEAD(unplug_list, unplug, node);
+}
+
+static int spapr_cpu_release(Object *obj, void *opaque)
+{
+    DeviceState *dev = DEVICE(obj);
+    CPUState *cs = CPU(dev);
+    PowerPCCPU *cpu = POWERPC_CPU(cs);
+    struct sPAPRCPUUnplugList *unplug_list = opaque;
+
+    spapr_cpu_destroy(cpu);
+    cpu_remove_sync(cs);
+
+    /*
+     * We are still walking the core object's children list, and
+     * hence can't cleanup this CPU thread object just yet. Put
+     * it on a list for later removal.
+     */
+    spapr_add_cpu_to_unplug_list(obj, unplug_list);
+    return 0;
+}
+
+static void spapr_core_release(DeviceState *dev, void *opaque)
+{
+    struct sPAPRCPUUnplugList unplug_list;
+    sPAPRMachineState *spapr = SPAPR_MACHINE(qdev_get_machine());
+    sPAPRCPUCore *core = SPAPR_CPU_CORE(OBJECT(dev));
+    CPUCore *cc = CPU_CORE(dev);
+    int smt = kvmppc_smt_threads();
+
+    QLIST_INIT(&unplug_list);
+    object_child_foreach(OBJECT(dev), spapr_cpu_release, &unplug_list);
+    spapr_cpu_core_cleanup(&unplug_list);
+    spapr->cores[cc->core / 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 = &core->threads[0];
+    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.h b/include/hw/ppc/spapr.h
index ca4ae3e..a443693 100644
--- a/include/hw/ppc/spapr.h
+++ b/include/hw/ppc/spapr.h
@@ -585,6 +585,7 @@ void spapr_hotplug_req_remove_by_count(sPAPRDRConnectorType drc_type,
 void spapr_cpu_init(sPAPRMachineState *spapr, PowerPCCPU *cpu, Error **errp);
 void *spapr_populate_hotplug_cpu_dt(CPUState *cs, int *fdt_offset,
                                     sPAPRMachineState *spapr);
+void spapr_cpu_destroy(PowerPCCPU *cpu);
 
 /* rtas-configure-connector state */
 struct sPAPRConfigureConnectorState {
diff --git a/include/hw/ppc/spapr_cpu_core.h b/include/hw/ppc/spapr_cpu_core.h
index 4cd837e..3d8d6ac 100644
--- a/include/hw/ppc/spapr_cpu_core.h
+++ b/include/hw/ppc/spapr_cpu_core.h
@@ -30,4 +30,15 @@ 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);
+
+/* List to store unplugged CPU objects for cleanup during unplug */
+typedef struct sPAPRCPUUnplug {
+    Object *cpu;
+    QLIST_ENTRY(sPAPRCPUUnplug) node;
+} sPAPRCPUUnplug;
+
+QLIST_HEAD(sPAPRCPUUnplugList, sPAPRCPUUnplug);
+
 #endif
-- 
2.1.0