Re: [Xen-devel] [PATCH v2 1/2] Add PCI bus listener interface

["Michael S. Tsirkin" <mst@xxxxxxxxxx>]

On Mon, Oct 13, 2014 at 01:52:46PM +0100, Paul Durrant wrote:
> 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@xxxxxxxxxx>
> Cc: Michael S. Tsirkin <mst@xxxxxxxxxx>
> Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx>
> Cc: Andreas Faerber <afaerber@xxxxxxx>
> Cc: Thomas Huth <thuth@xxxxxxxxxxxxxxxxxx>
> Cc: Peter Crosthwaite <peter.crosthwaite@xxxxxxxxxx>
> Cc: Christian Borntraeger <borntraeger@xxxxxxxxxx>

Do you really need multiple notifiers?

In any case, I think such a mechanism makes more sense on QOM level:
we have APIs to find objects of a given class and/or at a given path,
why not a mechanism to get notified when said objects are added/removed.



> ---
>  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

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