[PATCH RFC 16/22] arm/cpuhp: Add/update basic hot-(un)plug framework

[Salil Mehta]

Adds the new cpu hot-unplug hooks and updates the existing hotplug hooks with
sanity checks.

Note, Functional contents of the hooks(now left with TODO comment) shall be
gradually filled in the subsequent patches in an incremental approach to patch
and logic building which would be roughly as follows:
1. (Un-)wiring of interrupts between vcpu<->gic
2. Sending events to Guest for hot-(un)plug so that guest can take appropriate
   actions.
3. Notifying GIC about hot-(un)plug action so that vcpu could be (un-)stitched
   to the GIC CPU interface.
4. Updating the Guest with Next boot info for this vcpu in the firmware.

Co-developed-by: Keqian Zhu <zhukeqian1@huawei.com>
Signed-off-by: Salil Mehta <salil.mehta@huawei.com>
---
 hw/arm/virt.c | 102 +++++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 100 insertions(+), 2 deletions(-)

diff --git a/hw/arm/virt.c b/hw/arm/virt.c
index 0faf54aa8f..ac2941159a 100644
--- a/hw/arm/virt.c
+++ b/hw/arm/virt.c
@@ -2324,11 +2324,23 @@ out:
 static void virt_cpu_pre_plug(HotplugHandler *hotplug_dev, DeviceState *dev,
                               Error **errp)
 {
+    VirtMachineState *vms = VIRT_MACHINE(hotplug_dev);
     MachineState *ms = MACHINE(hotplug_dev);
     ARMCPU *cpu = ARM_CPU(dev);
     CPUState *cs = CPU(dev);
     CPUArchId *cpu_slot;
 
+    if (dev->hotplugged && !vms->acpi_dev) {
+        error_setg(errp, "GED acpi device does not exists");
+        return;
+    }
+
+    if (dev->hotplugged && (vms->gic_version < VIRT_GIC_VERSION_3)) {
+        error_setg(errp, "CPU hotplug not supported with GICv%d, use GICv3 or "
+                   "later", vms->gic_version);
+        return;
+    }
+
     /* sanity check the cpu */
     if (!object_dynamic_cast(OBJECT(cpu), ms->cpu_type)) {
         error_setg(errp, "Invalid CPU type, expected cpu type: '%s'",
@@ -2361,6 +2373,10 @@ static void virt_cpu_pre_plug(HotplugHandler 
*hotplug_dev, DeviceState *dev,
         return;
     }
     virt_cpu_set_properties(OBJECT(cs), cpu_slot);
+
+    if (dev->hotplugged) {
+        /* TODO: update GIC about this hotplug change here */
+    }
 }
 
 static void virt_cpu_plug(HotplugHandler *hotplug_dev, DeviceState *dev,
@@ -2375,10 +2391,75 @@ static void virt_cpu_plug(HotplugHandler *hotplug_dev, 
DeviceState *dev,
     cpu_slot = virt_find_cpu_slot(ms, cpu->core_id);
     cpu_slot->cpu = OBJECT(dev);
 
+    if (dev->hotplugged) {
+        /* TODO: wire the gic-cpu irqs */
+        /* TODO: update acpi hotplug state and send cpu hotplug event to guest 
*/
+        /* TODO: register this cpu for reset & update F/W info for the next 
boot */
+    }
+
     cs->disabled = false;
     return;
 }
 
+static void virt_cpu_unplug_request(HotplugHandler *hotplug_dev,
+                                    DeviceState *dev, Error **errp)
+{
+    VirtMachineState *vms = VIRT_MACHINE(hotplug_dev);
+    CPUState *cs = CPU(dev);
+
+    if (!vms->acpi_dev || !dev->realized) {
+        error_setg(errp, "GED does not exists or device is not realized!");
+        return;
+    }
+
+    if (vms->gic_version < VIRT_GIC_VERSION_3) {
+        error_setg(errp, "CPU hot-unplug not supported with GICv%d",
+                   vms->gic_version);
+        return;
+    }
+
+    if (cs->cpu_index == first_cpu->cpu_index)
+    {
+        error_setg(errp, "hot-unplug of ARM boot vcpu %d not supported",
+                   first_cpu->cpu_index);
+        return;
+    }
+
+    /* TODO: request cpu hotplug from guest */
+
+    return;
+}
+
+static void virt_cpu_unplug(HotplugHandler *hotplug_dev, DeviceState *dev,
+                            Error **errp)
+{
+    VirtMachineState *vms = VIRT_MACHINE(hotplug_dev);
+    MachineState *ms = MACHINE(hotplug_dev);
+    CPUState *cs = CPU(dev);
+    CPUArchId *cpu_slot;
+
+    if (!vms->acpi_dev || !dev->realized) {
+        error_setg(errp, "GED does not exists or device is not realized!");
+        return;
+    }
+
+    cpu_slot = virt_find_cpu_slot(ms, ARM_CPU(cs)->core_id);
+
+    /* TODO: update the acpi cpu hotplug state for cpu hot-unplug */
+
+    /* TODO: unwire the gic-cpu irqs here */
+    /* TODO: update the GIC about this hot unplug change */
+
+    /* TODO: unregister this cpu for reset & update F/W info for the next boot 
*/
+
+    qemu_opts_del(dev->opts);
+    dev->opts = NULL;
+
+    cpu_slot->cpu = NULL;
+    cs->disabled = true;
+    return;
+}
+
 static void virt_machine_device_pre_plug_cb(HotplugHandler *hotplug_dev,
                                             DeviceState *dev, Error **errp)
 {
@@ -2417,8 +2498,23 @@ static void virt_machine_device_plug_cb(HotplugHandler 
*hotplug_dev,
 static void virt_machine_device_unplug_request_cb(HotplugHandler *hotplug_dev,
                                           DeviceState *dev, Error **errp)
 {
-    error_setg(errp, "device unplug request for unsupported device"
-               " type: %s", object_get_typename(OBJECT(dev)));
+    if (object_dynamic_cast(OBJECT(dev), TYPE_CPU)) {
+        virt_cpu_unplug_request(hotplug_dev, dev, errp);
+    } else {
+        error_setg(errp, "device unplug request for unsupported type: %s",
+                   object_get_typename(OBJECT(dev)));
+    }
+}
+
+static void virt_machine_device_unplug_cb(HotplugHandler *hotplug_dev,
+                                          DeviceState *dev, Error **errp)
+{
+    if (object_dynamic_cast(OBJECT(dev), TYPE_CPU)) {
+        virt_cpu_unplug(hotplug_dev, dev, errp);
+    } else {
+        error_setg(errp, "device unplug for unsupported type: %s",
+                   object_get_typename(OBJECT(dev)));
+    }
 }
 
 static HotplugHandler *virt_machine_get_hotplug_handler(MachineState *machine,
@@ -2535,11 +2631,13 @@ static void virt_machine_class_init(ObjectClass *oc, 
void *data)
     mc->default_cpu_type = ARM_CPU_TYPE_NAME("cortex-a15");
     mc->get_default_cpu_node_id = virt_get_default_cpu_node_id;
     mc->kvm_type = virt_kvm_type;
+    mc->has_hotpluggable_cpus = true;
     assert(!mc->get_hotplug_handler);
     mc->get_hotplug_handler = virt_machine_get_hotplug_handler;
     hc->pre_plug = virt_machine_device_pre_plug_cb;
     hc->plug = virt_machine_device_plug_cb;
     hc->unplug_request = virt_machine_device_unplug_request_cb;
+    hc->unplug = virt_machine_device_unplug_cb;
     mc->numa_mem_supported = true;
     mc->nvdimm_supported = true;
     mc->auto_enable_numa_with_memhp = true;
-- 
2.17.1