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authorMarkus Armbruster <armbru@redhat.com>2020-05-05 17:29:24 +0200
committerMarkus Armbruster <armbru@redhat.com>2020-05-15 07:08:14 +0200
commitb69c3c21a5d11075d42100d5cfe0a736593fae6b (patch)
treeb34284892cb90e420c8ec9cb909686664052dcde /hw/pci
parent40c2281cc3342573bd72895997b5cfaddee36ef2 (diff)
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qdev: Unrealize must not fail
Devices may have component devices and buses. Device realization may fail. Realization is recursive: a device's realize() method realizes its components, and device_set_realized() realizes its buses (which should in turn realize the devices on that bus, except bus_set_realized() doesn't implement that, yet). When realization of a component or bus fails, we need to roll back: unrealize everything we realized so far. If any of these unrealizes failed, the device would be left in an inconsistent state. Must not happen. device_set_realized() lets it happen: it ignores errors in the roll back code starting at label child_realize_fail. Since realization is recursive, unrealization must be recursive, too. But how could a partly failed unrealize be rolled back? We'd have to re-realize, which can fail. This design is fundamentally broken. device_set_realized() does not roll back at all. Instead, it keeps unrealizing, ignoring further errors. It can screw up even for a device with no buses: if the lone dc->unrealize() fails, it still unregisters vmstate, and calls listeners' unrealize() callback. bus_set_realized() does not roll back either. Instead, it stops unrealizing. Fortunately, no unrealize method can fail, as we'll see below. To fix the design error, drop parameter @errp from all the unrealize methods. Any unrealize method that uses @errp now needs an update. This leads us to unrealize() methods that can fail. Merely passing it to another unrealize method cannot cause failure, though. Here are the ones that do other things with @errp: * virtio_serial_device_unrealize() Fails when qbus_set_hotplug_handler() fails, but still does all the other work. On failure, the device would stay realized with its resources completely gone. Oops. Can't happen, because qbus_set_hotplug_handler() can't actually fail here. Pass &error_abort to qbus_set_hotplug_handler() instead. * hw/ppc/spapr_drc.c's unrealize() Fails when object_property_del() fails, but all the other work is already done. On failure, the device would stay realized with its vmstate registration gone. Oops. Can't happen, because object_property_del() can't actually fail here. Pass &error_abort to object_property_del() instead. * spapr_phb_unrealize() Fails and bails out when remove_drcs() fails, but other work is already done. On failure, the device would stay realized with some of its resources gone. Oops. remove_drcs() fails only when chassis_from_bus()'s object_property_get_uint() fails, and it can't here. Pass &error_abort to remove_drcs() instead. Therefore, no unrealize method can fail before this patch. device_set_realized()'s recursive unrealization via bus uses object_property_set_bool(). Can't drop @errp there, so pass &error_abort. We similarly unrealize with object_property_set_bool() elsewhere, always ignoring errors. Pass &error_abort instead. Several unrealize methods no longer handle errors from other unrealize methods: virtio_9p_device_unrealize(), virtio_input_device_unrealize(), scsi_qdev_unrealize(), ... Much of the deleted error handling looks wrong anyway. One unrealize methods no longer ignore such errors: usb_ehci_pci_exit(). Several realize methods no longer ignore errors when rolling back: v9fs_device_realize_common(), pci_qdev_unrealize(), spapr_phb_realize(), usb_qdev_realize(), vfio_ccw_realize(), virtio_device_realize(). Signed-off-by: Markus Armbruster <armbru@redhat.com> Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com> Reviewed-by: Paolo Bonzini <pbonzini@redhat.com> Message-Id: <20200505152926.18877-17-armbru@redhat.com>
Diffstat (limited to 'hw/pci')
-rw-r--r--hw/pci/pci.c14
-rw-r--r--hw/pci/pcie.c2
-rw-r--r--hw/pci/shpc.c2
3 files changed, 9 insertions, 9 deletions
diff --git a/hw/pci/pci.c b/hw/pci/pci.c
index b5bc842..70c6696 100644
--- a/hw/pci/pci.c
+++ b/hw/pci/pci.c
@@ -146,7 +146,7 @@ static void pcie_bus_realize(BusState *qbus, Error **errp)
}
}
-static void pci_bus_unrealize(BusState *qbus, Error **errp)
+static void pci_bus_unrealize(BusState *qbus)
{
PCIBus *bus = PCI_BUS(qbus);
@@ -456,7 +456,7 @@ void pci_root_bus_cleanup(PCIBus *bus)
{
pci_bus_uninit(bus);
/* the caller of the unplug hotplug handler will delete this device */
- object_property_set_bool(OBJECT(bus), false, "realized", NULL);
+ object_property_set_bool(OBJECT(bus), false, "realized", &error_abort);
}
void pci_bus_irqs(PCIBus *bus, pci_set_irq_fn set_irq, pci_map_irq_fn map_irq,
@@ -1118,7 +1118,7 @@ static void pci_unregister_io_regions(PCIDevice *pci_dev)
pci_unregister_vga(pci_dev);
}
-static void pci_qdev_unrealize(DeviceState *dev, Error **errp)
+static void pci_qdev_unrealize(DeviceState *dev)
{
PCIDevice *pci_dev = PCI_DEVICE(dev);
PCIDeviceClass *pc = PCI_DEVICE_GET_CLASS(pci_dev);
@@ -2108,7 +2108,7 @@ static void pci_qdev_realize(DeviceState *qdev, Error **errp)
error_setg(errp, "failover primary device must be on "
"PCIExpress bus");
error_propagate(errp, local_err);
- pci_qdev_unrealize(DEVICE(pci_dev), NULL);
+ pci_qdev_unrealize(DEVICE(pci_dev));
return;
}
class_id = pci_get_word(pci_dev->config + PCI_CLASS_DEVICE);
@@ -2116,7 +2116,7 @@ static void pci_qdev_realize(DeviceState *qdev, Error **errp)
error_setg(errp, "failover primary device is not an "
"Ethernet device");
error_propagate(errp, local_err);
- pci_qdev_unrealize(DEVICE(pci_dev), NULL);
+ pci_qdev_unrealize(DEVICE(pci_dev));
return;
}
if (!(pci_dev->cap_present & QEMU_PCI_CAP_MULTIFUNCTION)
@@ -2126,7 +2126,7 @@ static void pci_qdev_realize(DeviceState *qdev, Error **errp)
error_setg(errp, "failover: primary device must be in its own "
"PCI slot");
error_propagate(errp, local_err);
- pci_qdev_unrealize(DEVICE(pci_dev), NULL);
+ pci_qdev_unrealize(DEVICE(pci_dev));
return;
}
qdev->allow_unplug_during_migration = true;
@@ -2142,7 +2142,7 @@ static void pci_qdev_realize(DeviceState *qdev, Error **errp)
pci_add_option_rom(pci_dev, is_default_rom, &local_err);
if (local_err) {
error_propagate(errp, local_err);
- pci_qdev_unrealize(DEVICE(pci_dev), NULL);
+ pci_qdev_unrealize(DEVICE(pci_dev));
return;
}
}
diff --git a/hw/pci/pcie.c b/hw/pci/pcie.c
index abc99b6..f50e10b 100644
--- a/hw/pci/pcie.c
+++ b/hw/pci/pcie.c
@@ -457,7 +457,7 @@ 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_property_set_bool(OBJECT(dev), false, "realized", NULL);
+ object_property_set_bool(OBJECT(dev), false, "realized", &error_abort);
}
static void pcie_unplug_device(PCIBus *bus, PCIDevice *dev, void *opaque)
diff --git a/hw/pci/shpc.c b/hw/pci/shpc.c
index 7f0aa28..b76d3d2 100644
--- a/hw/pci/shpc.c
+++ b/hw/pci/shpc.c
@@ -547,7 +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_property_set_bool(OBJECT(dev), false, "realized", NULL);
+ object_property_set_bool(OBJECT(dev), false, "realized", &error_abort);
}
void shpc_device_unplug_request_cb(HotplugHandler *hotplug_dev,