[Qemu-devel] [PATCH v1 0/3] qdev: Hotplug handler chaining

[Qemu-devel] [PATCH v1 0/3] qdev: Hotplug handler chaining

[David Hildenbrand]

This series implements support for hotplug handler chaining (proposed
by Igor), something that is necessary to turn selected virtio devices into
memory devices. Planned devices inlude virtio-mem and virtio-pmem.

The machine hotplug handler can intercept hotplug handler calls
to properly prepare/teardown the memory device part of a device. Control
is then passed on to the actual bus hotplug handler. So the default hotplug
handler is effectively overwritten to make interception possible.

This series was tested against
  [PATCH v3 0/6] tests: Add device unplug tests

RFCv2 -> v1:
- "qdev: Let the hotplug_handler_unplug() caller delete the device"
-- Fixed two spapr delete_device() calls I missed. Covered by tests now :)
-- Handle + add a comment for host pci bridge unplug, for which we have
   code but no user yet.
- virtio-pmem prototype will be handled from this point by Pankaj again,
  so no longer included

David Hildenbrand (2):
  qdev: Let the hotplug_handler_unplug() caller delete the device
  qdev: Provide qdev_get_bus_hotplug_handler()

Igor Mammedov (1):
  qdev: Let machine hotplug handler to override bus hotplug handler

 hw/acpi/cpu.c            |  1 +
 hw/acpi/memory_hotplug.c |  1 +
 hw/acpi/pcihp.c          |  3 ++-
 hw/core/qdev.c           | 19 ++++++++++++-------
 hw/i386/pc.c             |  5 ++---
 hw/pci/pci.c             |  3 ++-
 hw/pci/pcie.c            |  3 ++-
 hw/pci/shpc.c            |  3 ++-
 hw/ppc/spapr.c           |  6 ++++--
 hw/ppc/spapr_pci.c       |  3 ++-
 hw/s390x/css-bridge.c    |  2 +-
 hw/s390x/s390-pci-bus.c  | 13 ++++++++-----
 include/hw/qdev-core.h   | 12 ++++++++++++
 qdev-monitor.c           |  9 +++++++--
 14 files changed, 58 insertions(+), 25 deletions(-)

-- 
2.17.2

[Qemu-devel] [PATCH v1 1/3] qdev: Let the hotplug_handler_unplug() caller delete the device

[David Hildenbrand]

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>
---
 hw/acpi/cpu.c            |  1 +
 hw/acpi/memory_hotplug.c |  1 +
 hw/acpi/pcihp.c          |  3 ++-
 hw/core/qdev.c           |  3 +--
 hw/i386/pc.c             |  5 ++---
 hw/pci/pci.c             |  3 ++-
 hw/pci/pcie.c            |  3 ++-
 hw/pci/shpc.c            |  3 ++-
 hw/ppc/spapr.c           |  6 ++++--
 hw/ppc/spapr_pci.c       |  3 ++-
 hw/s390x/css-bridge.c    |  2 +-
 hw/s390x/s390-pci-bus.c  | 13 ++++++++-----
 qdev-monitor.c           |  9 +++++++--
 13 files changed, 35 insertions(+), 20 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 7bc7a72340..31b1a8fe58 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 d59071b8ed..278cc094ec 100644
--- a/hw/core/qdev.c
+++ b/hw/core/qdev.c
@@ -286,8 +286,7 @@ 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 3889eccdc3..30f15e352f 100644
--- a/hw/i386/pc.c
+++ b/hw/i386/pc.c
@@ -2181,8 +2181,7 @@ 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);
 }
@@ -2288,7 +2287,7 @@ 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 230478faab..9b829c8434 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 45053b39b9..44620ad845 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 332cba89d4..33ce5293da 100644
--- a/hw/ppc/spapr.c
+++ b/hw/ppc/spapr.c
@@ -3448,6 +3448,7 @@ 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)
@@ -3456,7 +3457,7 @@ 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);
 }
 
@@ -3541,6 +3542,7 @@ 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)
@@ -3563,7 +3565,7 @@ 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
diff --git a/hw/ppc/spapr_pci.c b/hw/ppc/spapr_pci.c
index c99721cde8..271fd4ac2c 100644
--- a/hw/ppc/spapr_pci.c
+++ b/hw/ppc/spapr_pci.c
@@ -1373,6 +1373,7 @@ 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,
@@ -1495,7 +1496,7 @@ 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 1bd6c8b458..614c2a3b8b 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 80ff1ce33f..ef5aee284c 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 07147c63bf..7705acd6c7 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)
-- 
2.17.2

[Qemu-devel] [PATCH v1 2/3] qdev: Let machine hotplug handler to override bus hotplug handler

[David Hildenbrand]

From: Igor Mammedov <imammedo@redhat.com>

it will allow to return another hotplug handler than the default
one for a specific bus based device type. Which is needed to handle
non trivial plug/unplug sequences that need the access to resources
configured outside of bus where device is attached.

That will allow for returned hotplug handler to orchestrate wiring
in arbitrary order, by chaining other hotplug handlers when
it's needed.

PS:
It could be used for hybrid virtio-mem and virtio-pmem devices
where it will return machine as hotplug handler which will do
necessary wiring at machine level and then pass control down
the chain to bus specific hotplug handler.

Example of top level hotplug handler override and custom plug sequence:

  some_machine_get_hotplug_handler(machine){
      if (object_dynamic_cast(OBJECT(dev), TYPE_SOME_BUS_DEVICE)) {
          return HOTPLUG_HANDLER(machine);
      }
      return NULL;
  }

  some_machine_device_plug(hotplug_dev, dev) {
      if (object_dynamic_cast(OBJECT(dev), TYPE_SOME_BUS_DEVICE)) {
          /* do machine specific initialization */
          some_machine_init_special_device(dev)

          /* pass control to bus specific handler */
          hotplug_handler_plug(dev->parent_bus->hotplug_handler, dev)
      }
  }

Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Igor Mammedov <imammedo@redhat.com>
Signed-off-by: David Hildenbrand <david@redhat.com>
---
 hw/core/qdev.c         |  6 ++----
 include/hw/qdev-core.h | 11 +++++++++++
 2 files changed, 13 insertions(+), 4 deletions(-)

diff --git a/hw/core/qdev.c b/hw/core/qdev.c
index 278cc094ec..7ad45c0bd6 100644
--- a/hw/core/qdev.c
+++ b/hw/core/qdev.c
@@ -235,12 +235,10 @@ HotplugHandler *qdev_get_machine_hotplug_handler(DeviceState *dev)
 
 HotplugHandler *qdev_get_hotplug_handler(DeviceState *dev)
 {
-    HotplugHandler *hotplug_ctrl;
+    HotplugHandler *hotplug_ctrl = qdev_get_machine_hotplug_handler(dev);
 
-    if (dev->parent_bus && dev->parent_bus->hotplug_handler) {
+    if (hotplug_ctrl == NULL && dev->parent_bus) {
         hotplug_ctrl = dev->parent_bus->hotplug_handler;
-    } else {
-        hotplug_ctrl = qdev_get_machine_hotplug_handler(dev);
     }
     return hotplug_ctrl;
 }
diff --git a/include/hw/qdev-core.h b/include/hw/qdev-core.h
index 0a84c42756..9081fb0030 100644
--- a/include/hw/qdev-core.h
+++ b/include/hw/qdev-core.h
@@ -281,6 +281,17 @@ void qdev_init_nofail(DeviceState *dev);
 void qdev_set_legacy_instance_id(DeviceState *dev, int alias_id,
                                  int required_for_version);
 HotplugHandler *qdev_get_machine_hotplug_handler(DeviceState *dev);
+/**
+ * qdev_get_hotplug_handler: Get handler responsible for device wiring
+ *
+ * Find HOTPLUG_HANDLER for @dev that provides [pre|un]plug callbacks for it.
+ *
+ * Note: in case @dev has a parent bus, it will be returned as handler unless
+ * machine handler overrides it.
+ *
+ * Returns: pointer to object that implements TYPE_HOTPLUG_HANDLER interface
+ *          or NULL if there aren't any.
+ */
 HotplugHandler *qdev_get_hotplug_handler(DeviceState *dev);
 void qdev_unplug(DeviceState *dev, Error **errp);
 void qdev_simple_device_unplug_cb(HotplugHandler *hotplug_dev,
-- 
2.17.2

[Qemu-devel] [PATCH v1 3/3] qdev: Provide qdev_get_bus_hotplug_handler()

[David Hildenbrand]

Let's use a wrapper instead of looking it up manually. This function can
than be reused when we explicitly want to have the bus hotplug handler
(e.g. when the bus hotplug handler was overwritten by the machine
hotplug handler).

Reviewed-by: Igor Mammedov <imammedo@redhat.com>
Signed-off-by: David Hildenbrand <david@redhat.com>
---
 hw/core/qdev.c         | 10 +++++++++-
 include/hw/qdev-core.h |  1 +
 2 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/hw/core/qdev.c b/hw/core/qdev.c
index 7ad45c0bd6..e2207d77a4 100644
--- a/hw/core/qdev.c
+++ b/hw/core/qdev.c
@@ -233,12 +233,20 @@ HotplugHandler *qdev_get_machine_hotplug_handler(DeviceState *dev)
     return NULL;
 }
 
+HotplugHandler *qdev_get_bus_hotplug_handler(DeviceState *dev)
+{
+    if (dev->parent_bus) {
+        return dev->parent_bus->hotplug_handler;
+    }
+    return NULL;
+}
+
 HotplugHandler *qdev_get_hotplug_handler(DeviceState *dev)
 {
     HotplugHandler *hotplug_ctrl = qdev_get_machine_hotplug_handler(dev);
 
     if (hotplug_ctrl == NULL && dev->parent_bus) {
-        hotplug_ctrl = dev->parent_bus->hotplug_handler;
+        hotplug_ctrl = qdev_get_bus_hotplug_handler(dev);
     }
     return hotplug_ctrl;
 }
diff --git a/include/hw/qdev-core.h b/include/hw/qdev-core.h
index 9081fb0030..cb0ec63c2d 100644
--- a/include/hw/qdev-core.h
+++ b/include/hw/qdev-core.h
@@ -280,6 +280,7 @@ DeviceState *qdev_try_create(BusState *bus, const char *name);
 void qdev_init_nofail(DeviceState *dev);
 void qdev_set_legacy_instance_id(DeviceState *dev, int alias_id,
                                  int required_for_version);
+HotplugHandler *qdev_get_bus_hotplug_handler(DeviceState *dev);
 HotplugHandler *qdev_get_machine_hotplug_handler(DeviceState *dev);
 /**
  * qdev_get_hotplug_handler: Get handler responsible for device wiring
-- 
2.17.2

Re: [Qemu-devel] [PATCH v1 0/3] qdev: Hotplug handler chaining

[David Hildenbrand]

On 18.02.19 11:12, David Hildenbrand wrote:
> This series implements support for hotplug handler chaining (proposed
> by Igor), something that is necessary to turn selected virtio devices into
> memory devices. Planned devices inlude virtio-mem and virtio-pmem.
> 
> The machine hotplug handler can intercept hotplug handler calls
> to properly prepare/teardown the memory device part of a device. Control
> is then passed on to the actual bus hotplug handler. So the default hotplug
> handler is effectively overwritten to make interception possible.
> 
> This series was tested against
>   [PATCH v3 0/6] tests: Add device unplug tests
> 
> RFCv2 -> v1:
> - "qdev: Let the hotplug_handler_unplug() caller delete the device"
> -- Fixed two spapr delete_device() calls I missed. Covered by tests now :)
> -- Handle + add a comment for host pci bridge unplug, for which we have
>    code but no user yet.
> - virtio-pmem prototype will be handled from this point by Pankaj again,
>   so no longer included

Are there any more comments? I will resend as soon as the latest spapr
PULL request gets merged, because one patch conflicts with patch #1.

> 
> David Hildenbrand (2):
>   qdev: Let the hotplug_handler_unplug() caller delete the device
>   qdev: Provide qdev_get_bus_hotplug_handler()
> 
> Igor Mammedov (1):
>   qdev: Let machine hotplug handler to override bus hotplug handler
> 
>  hw/acpi/cpu.c            |  1 +
>  hw/acpi/memory_hotplug.c |  1 +
>  hw/acpi/pcihp.c          |  3 ++-
>  hw/core/qdev.c           | 19 ++++++++++++-------
>  hw/i386/pc.c             |  5 ++---
>  hw/pci/pci.c             |  3 ++-
>  hw/pci/pcie.c            |  3 ++-
>  hw/pci/shpc.c            |  3 ++-
>  hw/ppc/spapr.c           |  6 ++++--
>  hw/ppc/spapr_pci.c       |  3 ++-
>  hw/s390x/css-bridge.c    |  2 +-
>  hw/s390x/s390-pci-bus.c  | 13 ++++++++-----
>  include/hw/qdev-core.h   | 12 ++++++++++++
>  qdev-monitor.c           |  9 +++++++--
>  14 files changed, 58 insertions(+), 25 deletions(-)
> 


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Thanks,

David / dhildenb