[Qemu-devel] [PATCH v2 1/2] Add PCI bus listener interface

[Paul Durrant <paul.durrant@citrix.com>]

The Xen ioreq-server API, introduced in Xen 4.5, requires that PCI device
models explicitly register with Xen for config space accesses. This patch
adds a PCI bus listener interface which can be used by the Xen interface
code to monitor PCI buses for arrival and departure of devices.

Signed-off-by: Paul Durrant <paul.durrant@citrix.com>
Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Andreas Faerber <afaerber@suse.de>
Cc: Thomas Huth <thuth@linux.vnet.ibm.com>
Cc: Peter Crosthwaite <peter.crosthwaite@xilinx.com>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
---
 hw/pci/pci.c            |   65 +++++++++++++++++++++++++++++++++++++++++++++++
 include/hw/pci/pci.h    |    9 +++++++
 include/qemu/typedefs.h |    1 +
 3 files changed, 75 insertions(+)

diff --git a/hw/pci/pci.c b/hw/pci/pci.c
index 6ce75aa..53c955d 100644
--- a/hw/pci/pci.c
+++ b/hw/pci/pci.c
@@ -122,6 +122,66 @@ static uint16_t pci_default_sub_device_id = PCI_SUBDEVICE_ID_QEMU;
 
 static QLIST_HEAD(, PCIHostState) pci_host_bridges;
 
+static QTAILQ_HEAD(pci_listeners, PCIListener) pci_listeners
+    = QTAILQ_HEAD_INITIALIZER(pci_listeners);
+
+enum ListenerDirection { Forward, Reverse };
+
+#define PCI_LISTENER_CALL(_callback, _direction, _args...)      \
+    do {                                                        \
+        PCIListener *_listener;                                 \
+                                                                \
+        switch (_direction) {                                   \
+        case Forward:                                           \
+            QTAILQ_FOREACH(_listener, &pci_listeners, link) {   \
+                if (_listener->_callback) {                     \
+                    _listener->_callback(_listener, ##_args);   \
+                }                                               \
+            }                                                   \
+            break;                                              \
+        case Reverse:                                           \
+            QTAILQ_FOREACH_REVERSE(_listener, &pci_listeners,   \
+                                   pci_listeners, link) {       \
+                if (_listener->_callback) {                     \
+                    _listener->_callback(_listener, ##_args);   \
+                }                                               \
+            }                                                   \
+            break;                                              \
+        default:                                                \
+            abort();                                            \
+        }                                                       \
+    } while (0)
+
+static int pci_listener_add(DeviceState *dev, void *opaque)
+{
+    if (object_dynamic_cast(OBJECT(dev), TYPE_PCI_DEVICE)) {
+        PCIDevice *pci_dev = PCI_DEVICE(dev);
+
+        PCI_LISTENER_CALL(device_add, Forward, pci_dev);
+    }
+
+    return 0;
+}
+
+void pci_listener_register(PCIListener *listener)
+{
+    PCIHostState *host;
+
+    QTAILQ_INSERT_TAIL(&pci_listeners, listener, link);
+
+    QLIST_FOREACH(host, &pci_host_bridges, next) {
+        PCIBus *bus = host->bus;
+
+        qbus_walk_children(&bus->qbus, NULL, NULL, pci_listener_add,
+                           NULL, NULL);
+    }
+}
+
+void pci_listener_unregister(PCIListener *listener)
+{
+    QTAILQ_REMOVE(&pci_listeners, listener, link);
+}
+
 static int pci_bar(PCIDevice *d, int reg)
 {
     uint8_t type;
@@ -795,6 +855,8 @@ static void pci_config_free(PCIDevice *pci_dev)
 
 static void do_pci_unregister_device(PCIDevice *pci_dev)
 {
+    PCI_LISTENER_CALL(device_del, Reverse, pci_dev);
+
     pci_dev->bus->devices[pci_dev->devfn] = NULL;
     pci_config_free(pci_dev);
 
@@ -878,6 +940,9 @@ static PCIDevice *do_pci_register_device(PCIDevice *pci_dev, PCIBus *bus,
     pci_dev->config_write = config_write;
     bus->devices[devfn] = pci_dev;
     pci_dev->version_id = 2; /* Current pci device vmstate version */
+
+    PCI_LISTENER_CALL(device_add, Forward, pci_dev);
+
     return pci_dev;
 }
 
diff --git a/include/hw/pci/pci.h b/include/hw/pci/pci.h
index c352c7b..6c21b37 100644
--- a/include/hw/pci/pci.h
+++ b/include/hw/pci/pci.h
@@ -303,6 +303,15 @@ struct PCIDevice {
     MSIVectorPollNotifier msix_vector_poll_notifier;
 };
 
+struct PCIListener {
+    void (*device_add)(PCIListener *listener, PCIDevice *pci_dev);
+    void (*device_del)(PCIListener *listener, PCIDevice *pci_dev);
+    QTAILQ_ENTRY(PCIListener) link;
+};
+
+void pci_listener_register(PCIListener *listener);
+void pci_listener_unregister(PCIListener *listener);
+
 void pci_register_bar(PCIDevice *pci_dev, int region_num,
                       uint8_t attr, MemoryRegion *memory);
 void pci_register_vga(PCIDevice *pci_dev, MemoryRegion *mem,
diff --git a/include/qemu/typedefs.h b/include/qemu/typedefs.h
index 04df51b..2b974c6 100644
--- a/include/qemu/typedefs.h
+++ b/include/qemu/typedefs.h
@@ -54,6 +54,7 @@ typedef struct PCIHostState PCIHostState;
 typedef struct PCIExpressHost PCIExpressHost;
 typedef struct PCIBus PCIBus;
 typedef struct PCIDevice PCIDevice;
+typedef struct PCIListener PCIListener;
 typedef struct PCIExpressDevice PCIExpressDevice;
 typedef struct PCIBridge PCIBridge;
 typedef struct PCIEAERMsg PCIEAERMsg;
-- 
1.7.10.4