[Qemu-ppc] [PATCH v5 09/10] spapr: CPU hot unplug support

[Bharata B Rao]

Support hot removal of CPU for sPAPR guests by sending the hot unplug
notification to the guest via EPOW interrupt. Release the vCPU object
after CPU hot unplug so that vCPU fd can be parked and reused.

Signed-off-by: Bharata B Rao <address@hidden>
---
 hw/ppc/spapr.c | 71 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 71 insertions(+)

diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
index 4434d45..6dca553 100644
--- a/hw/ppc/spapr.c
+++ b/hw/ppc/spapr.c
@@ -2401,11 +2401,82 @@ static void spapr_machine_device_plug(HotplugHandler 
*hotplug_dev,
     }
 }
 
+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);
+}
+
+static void spapr_cpu_release(DeviceState *dev, void *opaque)
+{
+    CPUState *cs;
+    int i;
+    int id = ppc_get_vcpu_dt_id(POWERPC_CPU(CPU(dev)));
+
+    for (i = id; i < id + smp_threads; i++) {
+        CPU_FOREACH(cs) {
+            PowerPCCPU *cpu = POWERPC_CPU(cs);
+
+            if (i == ppc_get_vcpu_dt_id(cpu)) {
+                spapr_cpu_destroy(cpu);
+                cpu_remove(cs);
+            }
+        }
+    }
+}
+
+static int spapr_cpu_unplug(HotplugHandler *hotplug_dev, DeviceState *dev,
+                             Error **errp)
+{
+    CPUState *cs = CPU(dev);
+    PowerPCCPU *cpu = POWERPC_CPU(cs);
+    int id = ppc_get_vcpu_dt_id(cpu);
+    int smt = kvmppc_smt_threads();
+    sPAPRDRConnector *drc =
+        spapr_dr_connector_by_id(SPAPR_DR_CONNECTOR_TYPE_CPU, id);
+    sPAPRDRConnectorClass *drck;
+    Error *local_err = NULL;
+
+    /*
+     * SMT threads return from here, only main thread (core) will
+     * continue and signal hot unplug event to the guest.
+     */
+    if ((id % smt) != 0) {
+        return 0;
+    }
+    g_assert(drc);
+
+    drck = SPAPR_DR_CONNECTOR_GET_CLASS(drc);
+    drck->detach(drc, dev, spapr_cpu_release, NULL, &local_err);
+    if (local_err) {
+        error_propagate(errp, local_err);
+        return -1;
+    }
+
+    /*
+     * In addition to hotplugged CPUs, send the hot-unplug notification
+     * interrupt to the guest for coldplugged CPUs started via -device
+     * option too.
+     */
+    spapr_hotplug_req_remove_by_index(drc);
+    return 0;
+}
+
 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_CPU)) {
+        if (!smc->dr_cpu_enabled) {
+            error_setg(errp, "CPU hot unplug not supported on this machine");
+            return;
+        }
+        spapr_cpu_unplug(hotplug_dev, dev, errp);
     }
 }
 
-- 
2.1.0