During any vCPU hot-(un)plug operation, the running guest VM must be notified
about the addition of a new vCPU or the removal of an existing vCPU. This
notification is handled via an ACPI GED event, which is eventually demultiplexed
into a vCPU hotplug event, and then further into a specific hot-(un)plug event
for the *targeted* vCPU.

Introduce the required ACPI calls into the existing hot-(un)plug hooks, allowing
ACPI GED events to be triggered from QEMU to the guest VM.

Co-developed-by: Keqian Zhu <zhukeqian1@huawei.com>
Signed-off-by: Keqian Zhu <zhukeqian1@huawei.com>
Signed-off-by: Salil Mehta <salil.mehta@huawei.com>
---
 hw/arm/virt.c | 39 ++++++++++++++++++++++++++++++++++++---
 1 file changed, 36 insertions(+), 3 deletions(-)

diff --git a/hw/arm/virt.c b/hw/arm/virt.c
index b1eba8de8c..15d9c2d8ac 100644
--- a/hw/arm/virt.c
+++ b/hw/arm/virt.c
@@ -3181,6 +3181,7 @@ static void virt_cpu_plug(HotplugHandler *hotplug_dev, DeviceState *dev,
 {
     VirtMachineState *vms = VIRT_MACHINE(hotplug_dev);
     CPUState *cs = CPU(dev);
+    Error *local_err = NULL;
     CPUArchId *cpu_slot;
 
     /* insert the cold/hot-plugged vcpu in the slot */
@@ -3213,8 +3214,18 @@ static void virt_cpu_plug(HotplugHandler *hotplug_dev, DeviceState *dev,
      * hot-plugged, the guest is also notified.
      */
     if (vms->acpi_dev) {
-        /* TODO: update acpi hotplug state. Send cpu hotplug event to guest */
+        HotplugHandlerClass *hhc;
+        /* update acpi hotplug state and send cpu hotplug event to guest */
+        hhc = HOTPLUG_HANDLER_GET_CLASS(vms->acpi_dev);
+        hhc->plug(HOTPLUG_HANDLER(vms->acpi_dev), dev, &local_err);
+        if (local_err) {
+            goto fail;
+        }
     }
+
+    return;
+fail:
+    error_propagate(errp, local_err);
 }
 
 static void virt_cpu_unplug_request(HotplugHandler *hotplug_dev,
@@ -3223,7 +3234,9 @@ static void virt_cpu_unplug_request(HotplugHandler *hotplug_dev,
     MachineClass *mc = MACHINE_GET_CLASS(qdev_get_machine());
     VirtMachineState *vms = VIRT_MACHINE(hotplug_dev);
     ARMCPU *cpu = ARM_CPU(dev);
+    HotplugHandlerClass *hhc;
     CPUState *cs = CPU(dev);
+    Error *local_err = NULL;
 
     if (!vms->acpi_dev) {
         error_setg(errp, "GED does not exists or device is not realized!");
@@ -3242,14 +3255,25 @@ static void virt_cpu_unplug_request(HotplugHandler *hotplug_dev,
         return;
     }
 
-    /* TODO: request cpu hotplug from guest */
+    /* request cpu hotplug from guest */
+    hhc = HOTPLUG_HANDLER_GET_CLASS(vms->acpi_dev);
+    hhc->unplug_request(HOTPLUG_HANDLER(vms->acpi_dev), dev, &local_err);
+    if (local_err) {
+        goto fail;
+    }
+
+    return;
+fail:
+    error_propagate(errp, local_err);
 }
 
 static void virt_cpu_unplug(HotplugHandler *hotplug_dev, DeviceState *dev,
                             Error **errp)
 {
     VirtMachineState *vms = VIRT_MACHINE(hotplug_dev);
+    HotplugHandlerClass *hhc;
     CPUState *cs = CPU(dev);
+    Error *local_err = NULL;
     CPUArchId *cpu_slot;
 
     if (!vms->acpi_dev) {
@@ -3259,7 +3283,12 @@ static void virt_cpu_unplug(HotplugHandler *hotplug_dev, DeviceState *dev,
 
     cpu_slot = virt_find_cpu_slot(cs);
 
-    /* TODO: update the acpi cpu hotplug state for cpu hot-unplug */
+    /* update the acpi cpu hotplug state for cpu hot-unplug */
+    hhc = HOTPLUG_HANDLER_GET_CLASS(vms->acpi_dev);
+    hhc->unplug(HOTPLUG_HANDLER(vms->acpi_dev), dev, &local_err);
+    if (local_err) {
+        goto fail;
+    }
 
     unwire_gic_cpu_irqs(vms, cs);
     virt_update_gic(vms, cs, false);
@@ -3274,6 +3303,10 @@ static void virt_cpu_unplug(HotplugHandler *hotplug_dev, DeviceState *dev,
     dev->opts = NULL;
 
     cpu_slot->cpu = NULL;
+
+    return;
+fail:
+    error_propagate(errp, local_err);
 }
 
 static void virt_machine_device_pre_plug_cb(HotplugHandler *hotplug_dev,
-- 
2.34.1