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

[Paul Durrant <Paul.Durrant@xxxxxxxxxx>]

> -----Original Message-----
> From: Michael S. Tsirkin [mailto:mst@xxxxxxxxxx]
> Sent: 14 October 2014 10:54
> To: Paul Durrant
> Cc: qemu-devel@xxxxxxxxxx; xen-devel@xxxxxxxxxxxxxxxxxxxx; Paolo
> Bonzini; Andreas Faerber; Thomas Huth; Peter Crosthwaite; Christian
> Borntraeger
> Subject: Re: [PATCH v2 1/2] Add PCI bus listener interface
> 
> 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?
> 

I don't quite understand what you mean by multiple notifiers. Are you 
suggesting that the PCI listener could be combined with the memory listener?

> 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.
> 

Having a general object listener could work as long as notifications could be 
filtered such that the Xen code could get notifications purely for PCI devices. 
The set of listeners clearly cannot be added to the object itself though, as 
you could then only register listeners after the object is created.

  Paul

> 
> 
> > ---
> >  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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