Re: [Xen-devel] [PATCH v3 1/2] Add device listener interface

[Igor Mammedov <imammedo@xxxxxxxxxx>]

On Wed, 15 Oct 2014 10:16:38 +0100
Paul Durrant <paul.durrant@xxxxxxxxxx> 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 listener interface into qdev-core which can be used
> by the Xen interface code to monitor for arrival and departure of PCI
> devices.

If you need only one listener handler for your case, why you couldn't
use hotplug interface instead of listerners?
to me it looks like it should work for this case.
To make it work xen code would need to override default plug/unplug
handlers on PCI bus and do register/unregister from there.

One thing is that unplug handler is not defined for PCI bus yet,
to get it work one would need to refactor pcihp/bridge/pcie unplug
path to call unplug handler before object_unparent().


> 
> Signed-off-by: Paul Durrant <paul.durrant@xxxxxxxxxx>
> Cc: Michael S. Tsirkin <mst@xxxxxxxxxx>
> Cc: Andreas Faerber" <afaerber@xxxxxxx>
> Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx>
> Cc: Peter Crosthwaite <peter.crosthwaite@xxxxxxxxxx>
> Cc: Igor Mammedov <imammedo@xxxxxxxxxx>
> Cc: Markus Armbruster <armbru@xxxxxxxxxx>
> Cc: Thomas Huth <thuth@xxxxxxxxxxxxxxxxxx>
> Cc: Christian Borntraeger <borntraeger@xxxxxxxxxx>
> ---
>  hw/core/qdev.c          |   54
> +++++++++++++++++++++++++++++++++++++++++++++++
> include/hw/qdev-core.h  |   10 +++++++++ include/qemu/typedefs.h |
> 1 + 3 files changed, 65 insertions(+)
> 
> diff --git a/hw/core/qdev.c b/hw/core/qdev.c
> index fcb1638..4a9c1f6 100644
> --- a/hw/core/qdev.c
> +++ b/hw/core/qdev.c
> @@ -175,6 +175,56 @@ int qdev_init(DeviceState *dev)
>      return 0;
>  }
>  
> +static QTAILQ_HEAD(qdev_listeners, DeviceListener) qdev_listeners
> +    = QTAILQ_HEAD_INITIALIZER(qdev_listeners);
> +
> +enum ListenerDirection { Forward, Reverse };
> +
> +#define QDEV_LISTENER_CALL(_callback, _direction, _args...)     \
> +    do {                                                        \
> +        DeviceListener *_listener;                              \
> +                                                                \
> +        switch (_direction) {                                   \
> +        case Forward:                                           \
> +            QTAILQ_FOREACH(_listener, &qdev_listeners, link) {  \
> +                if (_listener->_callback) {                     \
> +                    _listener->_callback(_listener, ##_args);   \
> +                }                                               \
> +            }                                                   \
> +            break;                                              \
> +        case Reverse:                                           \
> +            QTAILQ_FOREACH_REVERSE(_listener, &qdev_listeners,  \
> +                                   qdev_listeners, link) {      \
> +                if (_listener->_callback) {                     \
> +                    _listener->_callback(_listener, ##_args);   \
> +                }                                               \
> +            }                                                   \
> +            break;                                              \
> +        default:                                                \
> +            abort();                                            \
> +        }                                                       \
> +    } while (0)
> +
> +static int qdev_listener_add(DeviceState *dev, void *opaque)
> +{
> +    QDEV_LISTENER_CALL(realize, Forward, dev);
> +
> +    return 0;
> +}
> +
> +void qdev_listener_register(DeviceListener *listener)
> +{
> +    QTAILQ_INSERT_TAIL(&qdev_listeners, listener, link);
> +
> +    qbus_walk_children(sysbus_get_default(), NULL, NULL,
> qdev_listener_add,
> +                       NULL, NULL);
> +}
> +
> +void qdev_listener_unregister(DeviceListener *listener)
> +{
> +    QTAILQ_REMOVE(&qdev_listeners, listener, link);
> +}
> +
>  static void device_realize(DeviceState *dev, Error **errp)
>  {
>      DeviceClass *dc = DEVICE_GET_CLASS(dev);
> @@ -186,12 +236,16 @@ static void device_realize(DeviceState *dev,
> Error **errp) return;
>          }
>      }
> +
> +    QDEV_LISTENER_CALL(realize, Forward, dev);
>  }
>  
>  static void device_unrealize(DeviceState *dev, Error **errp)
>  {
>      DeviceClass *dc = DEVICE_GET_CLASS(dev);
>  
> +    QDEV_LISTENER_CALL(unrealize, Reverse, dev);
> +
>      if (dc->exit) {
>          int rc = dc->exit(dev);
>          if (rc < 0) {
> diff --git a/include/hw/qdev-core.h b/include/hw/qdev-core.h
> index 178fee2..f2dc267 100644
> --- a/include/hw/qdev-core.h
> +++ b/include/hw/qdev-core.h
> @@ -167,6 +167,12 @@ struct DeviceState {
>      int alias_required_for_version;
>  };
>  
> +struct DeviceListener {
> +    void (*realize)(DeviceListener *listener, DeviceState *dev);
> +    void (*unrealize)(DeviceListener *listener, DeviceState *dev);
> +    QTAILQ_ENTRY(DeviceListener) link;
> +};
> +
>  #define TYPE_BUS "bus"
>  #define BUS(obj) OBJECT_CHECK(BusState, (obj), TYPE_BUS)
>  #define BUS_CLASS(klass) OBJECT_CLASS_CHECK(BusClass, (klass),
> TYPE_BUS) @@ -368,4 +374,8 @@ static inline void
> qbus_set_hotplug_handler(BusState *bus, DeviceState *handler,
> QDEV_HOTPLUG_HANDLER_PROPERTY, errp); bus->allow_hotplug = 1;
>  }
> +
> +void qdev_listener_register(DeviceListener *listener);
> +void qdev_listener_unregister(DeviceListener *listener);
> +
>  #endif
> diff --git a/include/qemu/typedefs.h b/include/qemu/typedefs.h
> index 04df51b..e32bca2 100644
> --- a/include/qemu/typedefs.h
> +++ b/include/qemu/typedefs.h
> @@ -20,6 +20,7 @@ typedef struct Property Property;
>  typedef struct PropertyInfo PropertyInfo;
>  typedef struct CompatProperty CompatProperty;
>  typedef struct DeviceState DeviceState;
> +typedef struct DeviceListener DeviceListener;
>  typedef struct BusState BusState;
>  typedef struct BusClass BusClass;
>  


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