qdev: Let the hotplug_handler_unplug() caller delete the device

When unplugging a device, at one point the device will be destroyed
via object_unparent(). This will, one the one hand, unrealize the
removed device hierarchy, and on the other hand, destroy/free the
device hierarchy.

When chaining hotplug handlers, we want to overwrite a bus hotplug
handler by the machine hotplug handler, to be able to perform
some part of the plug/unplug and to forward the calls to the bus hotplug
handler.

For now, the bus hotplug handler would trigger an object_unparent(), not
allowing us to perform some unplug action on a device after we forwarded
the call to the bus hotplug handler. The device would be gone at that
point.

machine_unplug_handler(dev)
    /* eventually do unplug stuff */
    bus_unplug_handler(dev)
    /* dev is gone, we can't do more unplug stuff */

So move the object_unparent() to the original caller of the unplug. For
now, keep the unrealize() at the original places of the
object_unparent(). For implicitly chained hotplug handlers (e.g. pc
code calling acpi hotplug handlers), the object_unparent() has to be
done by the outermost caller. So when calling hotplug_handler_unplug()
from inside an unplug handler, nothing is to be done.

hotplug_handler_unplug(dev) -> calls machine_unplug_handler()
    machine_unplug_handler(dev) {
        /* eventually do unplug stuff */
        bus_unplug_handler(dev) -> calls unrealize(dev)
        /* we can do more unplug stuff but device already unrealized */
    }
object_unparent(dev)

In the long run, every unplug action should be factored out of the
unrealize() function into the unplug handler (especially for PCI). Then
we can get rid of the additonal unrealize() calls and object_unparent()
will properly unrealize the device hierarchy after the device has been
unplugged.

hotplug_handler_unplug(dev) -> calls machine_unplug_handler()
    machine_unplug_handler(dev) {
        /* eventually do unplug stuff */
        bus_unplug_handler(dev) -> only unplugs, does not unrealize
        /* we can do more unplug stuff */
    }
object_unparent(dev) -> will unrealize

The original approach was suggested by Igor Mammedov for the PCI
part, but I extended it to all hotplug handlers. I consider this one
step into the right direction.

To summarize:
- object_unparent() on synchronous unplugs is done by common code
-- "Caller of hotplug_handler_unplug"
- object_unparent() on asynchronous unplugs ("unplug requests") has to
  be done manually
-- "Caller of hotplug_handler_unplug"

Reviewed-by: Igor Mammedov <imammedo@redhat.com>
Acked-by: Cornelia Huck <cohuck@redhat.com>
Signed-off-by: David Hildenbrand <david@redhat.com>
Message-Id: <20190228122849.4296-2-david@redhat.com>
Reviewed-by: Greg Kurz <groug@kaod.org>
Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>

13 files changed, 37 insertions, 21 deletions

diff --git a/hw/acpi/cpu.c b/hw/acpi/cpu.c
index a0a43fe6b5..7a90c8f82d 100644
--- a/hw/acpi/cpu.c
+++ b/hw/acpi/cpu.c
@@ -126,6 +126,7 @@ static void cpu_hotplug_wr(void *opaque, hwaddr addr, uint64_t data,
             dev = DEVICE(cdev->cpu);
             hotplug_ctrl = qdev_get_hotplug_handler(dev);
             hotplug_handler_unplug(hotplug_ctrl, dev, NULL);
+            object_unparent(OBJECT(dev));
         }
         break;
     case ACPI_CPU_CMD_OFFSET_WR:
diff --git a/hw/acpi/memory_hotplug.c b/hw/acpi/memory_hotplug.c
index 921cad2c5e..297812d5f7 100644
--- a/hw/acpi/memory_hotplug.c
+++ b/hw/acpi/memory_hotplug.c
@@ -189,6 +189,7 @@ static void acpi_memory_hotplug_write(void *opaque, hwaddr addr, uint64_t data,
                 error_free(local_err);
                 break;
             }
+            object_unparent(OBJECT(dev));
             trace_mhp_acpi_pc_dimm_deleted(mem_st->selector);
         }
         break;
diff --git a/hw/acpi/pcihp.c b/hw/acpi/pcihp.c
index 9429181323..88e4ae1bcd 100644
--- a/hw/acpi/pcihp.c
+++ b/hw/acpi/pcihp.c
@@ -174,6 +174,7 @@ static void acpi_pcihp_eject_slot(AcpiPciHpState *s, unsigned bsel, unsigned slo
             if (!acpi_pcihp_pc_no_hotplug(s, dev)) {
                 hotplug_ctrl = qdev_get_hotplug_handler(qdev);
                 hotplug_handler_unplug(hotplug_ctrl, qdev, &error_abort);
+                object_unparent(OBJECT(qdev));
             }
         }
     }
@@ -269,7 +270,7 @@ void acpi_pcihp_device_plug_cb(HotplugHandler *hotplug_dev, AcpiPciHpState *s,
 void acpi_pcihp_device_unplug_cb(HotplugHandler *hotplug_dev, AcpiPciHpState *s,
                                  DeviceState *dev, Error **errp)
 {
-    object_unparent(OBJECT(dev));
+    object_property_set_bool(OBJECT(dev), false, "realized", NULL);
 }
 
 void acpi_pcihp_device_unplug_request_cb(HotplugHandler *hotplug_dev,
diff --git a/hw/core/qdev.c b/hw/core/qdev.c
index 00a5a39c76..a9647d42ae 100644
--- a/hw/core/qdev.c
+++ b/hw/core/qdev.c
@@ -289,8 +289,7 @@ void qbus_reset_all_fn(void *opaque)
 void qdev_simple_device_unplug_cb(HotplugHandler *hotplug_dev,
                                   DeviceState *dev, Error **errp)
 {
-    /* just zap it */
-    object_unparent(OBJECT(dev));
+    object_property_set_bool(OBJECT(dev), false, "realized", NULL);
 }
 
 /*
diff --git a/hw/i386/pc.c b/hw/i386/pc.c
index 578f772e7c..42128183e9 100644
--- a/hw/i386/pc.c
+++ b/hw/i386/pc.c
@@ -2154,8 +2154,7 @@ static void pc_memory_unplug(HotplugHandler *hotplug_dev,
     }
 
     pc_dimm_unplug(PC_DIMM(dev), MACHINE(pcms));
-    object_unparent(OBJECT(dev));
-
+    object_property_set_bool(OBJECT(dev), false, "realized", NULL);
  out:
     error_propagate(errp, local_err);
 }
@@ -2261,7 +2260,7 @@ static void pc_cpu_unplug_cb(HotplugHandler *hotplug_dev,
 
     found_cpu = pc_find_cpu_slot(MACHINE(pcms), cpu->apic_id, NULL);
     found_cpu->cpu = NULL;
-    object_unparent(OBJECT(dev));
+    object_property_set_bool(OBJECT(dev), false, "realized", NULL);
 
     /* decrement the number of CPUs */
     pcms->boot_cpus--;
diff --git a/hw/pci/pci.c b/hw/pci/pci.c
index c9fc2fbe19..35451c1e99 100644
--- a/hw/pci/pci.c
+++ b/hw/pci/pci.c
@@ -428,7 +428,8 @@ PCIBus *pci_root_bus_new(DeviceState *parent, const char *name,
 void pci_root_bus_cleanup(PCIBus *bus)
 {
     pci_bus_uninit(bus);
-    object_unparent(OBJECT(bus));
+    /* the caller of the unplug hotplug handler will delete this device */
+    object_property_set_bool(OBJECT(bus), false, "realized", NULL);
 }
 
 void pci_bus_irqs(PCIBus *bus, pci_set_irq_fn set_irq, pci_map_irq_fn map_irq,
diff --git a/hw/pci/pcie.c b/hw/pci/pcie.c
index 3618d6ab2e..640f678773 100644
--- a/hw/pci/pcie.c
+++ b/hw/pci/pcie.c
@@ -450,7 +450,7 @@ void pcie_cap_slot_plug_cb(HotplugHandler *hotplug_dev, DeviceState *dev,
 void pcie_cap_slot_unplug_cb(HotplugHandler *hotplug_dev, DeviceState *dev,
                              Error **errp)
 {
-    object_unparent(OBJECT(dev));
+    object_property_set_bool(OBJECT(dev), false, "realized", NULL);
 }
 
 static void pcie_unplug_device(PCIBus *bus, PCIDevice *dev, void *opaque)
@@ -458,6 +458,7 @@ static void pcie_unplug_device(PCIBus *bus, PCIDevice *dev, void *opaque)
     HotplugHandler *hotplug_ctrl = qdev_get_hotplug_handler(DEVICE(dev));
 
     hotplug_handler_unplug(hotplug_ctrl, DEVICE(dev), &error_abort);
+    object_unparent(OBJECT(dev));
 }
 
 void pcie_cap_slot_unplug_request_cb(HotplugHandler *hotplug_dev,
diff --git a/hw/pci/shpc.c b/hw/pci/shpc.c
index 52ccdc5ae3..49bbb841bd 100644
--- a/hw/pci/shpc.c
+++ b/hw/pci/shpc.c
@@ -249,6 +249,7 @@ static void shpc_free_devices_in_slot(SHPCDevice *shpc, int slot)
             hotplug_ctrl = qdev_get_hotplug_handler(DEVICE(affected_dev));
             hotplug_handler_unplug(hotplug_ctrl, DEVICE(affected_dev),
                                    &error_abort);
+            object_unparent(OBJECT(affected_dev));
         }
     }
 }
@@ -546,7 +547,7 @@ void shpc_device_plug_cb(HotplugHandler *hotplug_dev, DeviceState *dev,
 void shpc_device_unplug_cb(HotplugHandler *hotplug_dev, DeviceState *dev,
                            Error **errp)
 {
-    object_unparent(OBJECT(dev));
+    object_property_set_bool(OBJECT(dev), false, "realized", NULL);
 }
 
 void shpc_device_unplug_request_cb(HotplugHandler *hotplug_dev,
diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
index d7850ada7d..9e01226e18 100644
--- a/hw/ppc/spapr.c
+++ b/hw/ppc/spapr.c
@@ -3595,6 +3595,7 @@ void spapr_lmb_release(DeviceState *dev)
      * unplug handler chain. This can never fail.
      */
     hotplug_handler_unplug(hotplug_ctrl, dev, &error_abort);
+    object_unparent(OBJECT(dev));
 }
 
 static void spapr_memory_unplug(HotplugHandler *hotplug_dev, DeviceState *dev)
@@ -3603,7 +3604,7 @@ static void spapr_memory_unplug(HotplugHandler *hotplug_dev, DeviceState *dev)
     sPAPRDIMMState *ds = spapr_pending_dimm_unplugs_find(spapr, PC_DIMM(dev));
 
     pc_dimm_unplug(PC_DIMM(dev), MACHINE(hotplug_dev));
-    object_unparent(OBJECT(dev));
+    object_property_set_bool(OBJECT(dev), false, "realized", NULL);
     spapr_pending_dimm_unplugs_remove(spapr, ds);
 }
 
@@ -3667,6 +3668,7 @@ void spapr_core_release(DeviceState *dev)
 
     /* Call the unplug handler chain. This can never fail. */
     hotplug_handler_unplug(hotplug_ctrl, dev, &error_abort);
+    object_unparent(OBJECT(dev));
 }
 
 static void spapr_core_unplug(HotplugHandler *hotplug_dev, DeviceState *dev)
@@ -3689,7 +3691,7 @@ static void spapr_core_unplug(HotplugHandler *hotplug_dev, DeviceState *dev)
 
     assert(core_slot);
     core_slot->cpu = NULL;
-    object_unparent(OBJECT(dev));
+    object_property_set_bool(OBJECT(dev), false, "realized", NULL);
 }
 
 static
@@ -3940,11 +3942,12 @@ void spapr_phb_release(DeviceState *dev)
     HotplugHandler *hotplug_ctrl = qdev_get_hotplug_handler(dev);
 
     hotplug_handler_unplug(hotplug_ctrl, dev, &error_abort);
+    object_unparent(OBJECT(dev));
 }
 
 static void spapr_phb_unplug(HotplugHandler *hotplug_dev, DeviceState *dev)
 {
-    object_unparent(OBJECT(dev));
+    object_property_set_bool(OBJECT(dev), false, "realized", NULL);
 }
 
 static void spapr_phb_unplug_request(HotplugHandler *hotplug_dev,
diff --git a/hw/ppc/spapr_pci.c b/hw/ppc/spapr_pci.c
index 06a5ffd281..69059c36eb 100644
--- a/hw/ppc/spapr_pci.c
+++ b/hw/ppc/spapr_pci.c
@@ -1379,6 +1379,7 @@ void spapr_phb_remove_pci_device_cb(DeviceState *dev)
     HotplugHandler *hotplug_ctrl = qdev_get_hotplug_handler(dev);
 
     hotplug_handler_unplug(hotplug_ctrl, dev, &error_abort);
+    object_unparent(OBJECT(dev));
 }
 
 static sPAPRDRConnector *spapr_phb_get_pci_func_drc(sPAPRPHBState *phb,
@@ -1506,7 +1507,7 @@ static void spapr_pci_unplug(HotplugHandler *plug_handler,
      * an 'idle' state, as the device cleanup code expects.
      */
     pci_device_reset(PCI_DEVICE(plugged_dev));
-    object_unparent(OBJECT(plugged_dev));
+    object_property_set_bool(OBJECT(plugged_dev), false, "realized", NULL);
 }
 
 static void spapr_pci_unplug_request(HotplugHandler *plug_handler,
diff --git a/hw/s390x/css-bridge.c b/hw/s390x/css-bridge.c
index 7573c40bad..e04d51b191 100644
--- a/hw/s390x/css-bridge.c
+++ b/hw/s390x/css-bridge.c
@@ -51,7 +51,7 @@ static void ccw_device_unplug(HotplugHandler *hotplug_dev,
 
     css_generate_sch_crws(sch->cssid, sch->ssid, sch->schid, 1, 0);
 
-    object_unparent(OBJECT(dev));
+    object_property_set_bool(OBJECT(dev), false, "realized", NULL);
 }
 
 static void virtual_css_bus_reset(BusState *qbus)
diff --git a/hw/s390x/s390-pci-bus.c b/hw/s390x/s390-pci-bus.c
index 5998942b4c..2d0a28d544 100644
--- a/hw/s390x/s390-pci-bus.c
+++ b/hw/s390x/s390-pci-bus.c
@@ -154,14 +154,17 @@ static void s390_pci_perform_unplug(S390PCIBusDevice *pbdev)
 
     /* Unplug the PCI device */
     if (pbdev->pdev) {
-        hotplug_ctrl = qdev_get_hotplug_handler(DEVICE(pbdev->pdev));
-        hotplug_handler_unplug(hotplug_ctrl, DEVICE(pbdev->pdev),
-                               &error_abort);
+        DeviceState *pdev = DEVICE(pbdev->pdev);
+
+        hotplug_ctrl = qdev_get_hotplug_handler(pdev);
+        hotplug_handler_unplug(hotplug_ctrl, pdev, &error_abort);
+        object_unparent(OBJECT(pdev));
     }
 
     /* Unplug the zPCI device */
     hotplug_ctrl = qdev_get_hotplug_handler(DEVICE(pbdev));
     hotplug_handler_unplug(hotplug_ctrl, DEVICE(pbdev), &error_abort);
+    object_unparent(OBJECT(pbdev));
 }
 
 void s390_pci_sclp_deconfigure(SCCB *sccb)
@@ -994,7 +997,7 @@ static void s390_pcihost_unplug(HotplugHandler *hotplug_dev, DeviceState *dev,
                                      pbdev->fh, pbdev->fid);
         bus = pci_get_bus(pci_dev);
         devfn = pci_dev->devfn;
-        object_unparent(OBJECT(pci_dev));
+        object_property_set_bool(OBJECT(dev), false, "realized", NULL);
 
         s390_pci_msix_free(pbdev);
         s390_pci_iommu_free(s, bus, devfn);
@@ -1005,7 +1008,7 @@ static void s390_pcihost_unplug(HotplugHandler *hotplug_dev, DeviceState *dev,
         pbdev->fid = 0;
         QTAILQ_REMOVE(&s->zpci_devs, pbdev, link);
         g_hash_table_remove(s->zpci_table, &pbdev->idx);
-        object_unparent(OBJECT(pbdev));
+        object_property_set_bool(OBJECT(dev), false, "realized", NULL);
     }
 }
 
diff --git a/qdev-monitor.c b/qdev-monitor.c
index 45a8ba4964..d4320986a2 100644
--- a/qdev-monitor.c
+++ b/qdev-monitor.c
@@ -862,6 +862,7 @@ void qdev_unplug(DeviceState *dev, Error **errp)
     DeviceClass *dc = DEVICE_GET_CLASS(dev);
     HotplugHandler *hotplug_ctrl;
     HotplugHandlerClass *hdc;
+    Error *local_err = NULL;
 
     if (dev->parent_bus && !qbus_is_hotpluggable(dev->parent_bus)) {
         error_setg(errp, QERR_BUS_NO_HOTPLUG, dev->parent_bus->name);
@@ -890,10 +891,14 @@ void qdev_unplug(DeviceState *dev, Error **errp)
      * otherwise just remove it synchronously */
     hdc = HOTPLUG_HANDLER_GET_CLASS(hotplug_ctrl);
     if (hdc->unplug_request) {
-        hotplug_handler_unplug_request(hotplug_ctrl, dev, errp);
+        hotplug_handler_unplug_request(hotplug_ctrl, dev, &local_err);
     } else {
-        hotplug_handler_unplug(hotplug_ctrl, dev, errp);
+        hotplug_handler_unplug(hotplug_ctrl, dev, &local_err);
+        if (!local_err) {
+            object_unparent(OBJECT(dev));
+        }
     }
+    error_propagate(errp, local_err);
 }
 
 void qmp_device_del(const char *id, Error **errp)