pci: allow cleanup/unregistration of PCI root buses

This adds cleanup counterparts to pci_register_root_bus(),
pci_root_bus_new(), and pci_bus_irqs().

These cleanup routines are needed in the case of hotpluggable
PCIHostBridge implementations. Currently we can rely on the
object_unparent()'ing of the PCIHostState recursively unparenting
and cleaning up it's child buses, but we need explicit calls
to also:

  1) remove the PCIHostState from pci_host_bridges global list.
     otherwise, we risk accessing freed memory when we access
     the list later
  2) clean up memory allocated in pci_bus_irqs()

Both are handled outside the context of any particular bus or
host bridge's init/realize functions, making it difficult to
avoid the need for explicit cleanup functions without remodeling
how PCIHostBridges are created. So keep it simple and just add
them for now.

Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Greg Kurz <groug@kaod.org>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>

hw/pci/pci.c

@@ -333,6 +333,13 @@ static void pci_host_bus_register(DeviceState *host)
     QLIST_INSERT_HEAD(&pci_host_bridges, host_bridge, next);
 }
 
+static void pci_host_bus_unregister(DeviceState *host)
+{
+    PCIHostState *host_bridge = PCI_HOST_BRIDGE(host);
+
+    QLIST_REMOVE(host_bridge, next);
+}
+
 PCIBus *pci_device_root_bus(const PCIDevice *d)
 {
     PCIBus *bus = pci_get_bus(d);
@@ -379,6 +386,11 @@ static void pci_root_bus_init(PCIBus *bus, DeviceState *parent,
     pci_host_bus_register(parent);
 }
 
+static void pci_bus_uninit(PCIBus *bus)
+{
+    pci_host_bus_unregister(BUS(bus)->parent);
+}
+
 bool pci_bus_is_express(PCIBus *bus)
 {
     return object_dynamic_cast(OBJECT(bus), TYPE_PCIE_BUS);
@@ -413,6 +425,12 @@ PCIBus *pci_root_bus_new(DeviceState *parent, const char *name,
     return bus;
 }
 
+void pci_root_bus_cleanup(PCIBus *bus)
+{
+    pci_bus_uninit(bus);
+    object_unparent(OBJECT(bus));
+}
+
 void pci_bus_irqs(PCIBus *bus, pci_set_irq_fn set_irq, pci_map_irq_fn map_irq,
                   void *irq_opaque, int nirq)
 {
@@ -423,6 +441,15 @@ void pci_bus_irqs(PCIBus *bus, pci_set_irq_fn set_irq, pci_map_irq_fn map_irq,
     bus->irq_count = g_malloc0(nirq * sizeof(bus->irq_count[0]));
 }
 
+void pci_bus_irqs_cleanup(PCIBus *bus)
+{
+    bus->set_irq = NULL;
+    bus->map_irq = NULL;
+    bus->irq_opaque = NULL;
+    bus->nirq = 0;
+    g_free(bus->irq_count);
+}
+
 PCIBus *pci_register_root_bus(DeviceState *parent, const char *name,
                               pci_set_irq_fn set_irq, pci_map_irq_fn map_irq,
                               void *irq_opaque,
@@ -439,6 +466,12 @@ PCIBus *pci_register_root_bus(DeviceState *parent, const char *name,
     return bus;
 }
 
+void pci_unregister_root_bus(PCIBus *bus)
+{
+    pci_bus_irqs_cleanup(bus);
+    pci_root_bus_cleanup(bus);
+}
+
 int pci_bus_num(PCIBus *s)
 {
     return PCI_BUS_GET_CLASS(s)->bus_num(s);

include/hw/pci/pci.h

@@ -405,8 +405,10 @@ PCIBus *pci_root_bus_new(DeviceState *parent, const char *name,
                          MemoryRegion *address_space_mem,
                          MemoryRegion *address_space_io,
                          uint8_t devfn_min, const char *typename);
+void pci_root_bus_cleanup(PCIBus *bus);
 void pci_bus_irqs(PCIBus *bus, pci_set_irq_fn set_irq, pci_map_irq_fn map_irq,
                   void *irq_opaque, int nirq);
+void pci_bus_irqs_cleanup(PCIBus *bus);
 int pci_bus_get_irq_level(PCIBus *bus, int irq_num);
 /* 0 <= pin <= 3 0 = INTA, 1 = INTB, 2 = INTC, 3 = INTD */
 int pci_swizzle_map_irq_fn(PCIDevice *pci_dev, int pin);
@@ -417,6 +419,7 @@ PCIBus *pci_register_root_bus(DeviceState *parent, const char *name,
                               MemoryRegion *address_space_io,
                               uint8_t devfn_min, int nirq,
                               const char *typename);
+void pci_unregister_root_bus(PCIBus *bus);
 void pci_bus_set_route_irq_fn(PCIBus *, pci_route_irq_fn);
 PCIINTxRoute pci_device_route_intx_to_irq(PCIDevice *dev, int pin);
 bool pci_intx_route_changed(PCIINTxRoute *old, PCIINTxRoute *new);