Re: [Qemu-devel] [PATCH 07/10] pci: introduce pci bus pre reset

["Michael S. Tsirkin" <mst@redhat.com>]

On Wed, Feb 17, 2016 at 06:43:51PM +0800, Cao jin wrote:
> From: Chen Fan <chen.fan.fnst@cn.fujitsu.com>
> 
> avoid repeat bus reset, here introduce a sequence ID for each time
> bus hot reset, so each vfio device could know whether they've already
> been reset for that sequence ID.
> 
> Signed-off-by: Chen Fan <chen.fan.fnst@cn.fujitsu.com>

If the assumption that vfio functions are combined
in the same way as on the host, then this is not needed:
just reset when function 0 is reset.

I suggest we do it this way at stage one.
Add more checks when the functionality is in place.

> ---
>  hw/core/qdev.c           |  4 ++--
>  hw/pci/pci.c             | 25 +++++++++++++++++++++++++
>  hw/pci/pci_bridge.c      |  5 ++++-
>  include/hw/pci/pci_bus.h |  4 ++++
>  include/hw/qdev-core.h   |  3 +++
>  5 files changed, 38 insertions(+), 3 deletions(-)
> 
> diff --git a/hw/core/qdev.c b/hw/core/qdev.c
> index 779de2b..e36fa07 100644
> --- a/hw/core/qdev.c
> +++ b/hw/core/qdev.c
> @@ -304,14 +304,14 @@ void qdev_unplug(DeviceState *dev, Error **errp)
>      }
>  }
>  
> -static int qdev_reset_one(DeviceState *dev, void *opaque)
> +int qdev_reset_one(DeviceState *dev, void *opaque)
>  {
>      device_reset(dev);
>  
>      return 0;
>  }
>  
> -static int qbus_reset_one(BusState *bus, void *opaque)
> +int qbus_reset_one(BusState *bus, void *opaque)
>  {
>      BusClass *bc = BUS_GET_CLASS(bus);
>      if (bc->reset) {
> diff --git a/hw/pci/pci.c b/hw/pci/pci.c
> index e41925e..ff978bc 100644
> --- a/hw/pci/pci.c
> +++ b/hw/pci/pci.c
> @@ -258,6 +258,29 @@ void pci_device_reset(PCIDevice *dev)
>      pci_do_device_reset(dev);
>  }
>  
> +int pcibus_pre_reset(BusState *qbus, void *opaque)
> +{
> +    BusState *bus = (BusState *)opaque;
> +    PCIBus *pci_bus = DO_UPCAST(PCIBus, qbus, qbus);
> +    static unsigned int reset_seqid;
> +
> +    /*
> +     * To distinguish the different reset times, we
> +     * recalculate the global reset seqid with a given bus.
> +     */
> +    if (qbus == bus) {
> +        reset_seqid++;
> +        if (!reset_seqid) {
> +            reset_seqid = 1;
> +	}
> +    }
> +
> +    pci_bus->bus_in_reset = true;
> +    pci_bus->reset_seqid = reset_seqid;
> +
> +    return 0;
> +}
> +
>  /*
>   * Trigger pci bus reset under a given bus.
>   * Called via qbus_reset_all on RST# assert, after the devices
> @@ -277,6 +300,8 @@ static void pcibus_reset(BusState *qbus)
>      for (i = 0; i < bus->nirq; i++) {
>          assert(bus->irq_count[i] == 0);
>      }
> +
> +    bus->bus_in_reset = false;
>  }
>  
>  static void pci_host_bus_register(PCIBus *bus, DeviceState *parent)
> diff --git a/hw/pci/pci_bridge.c b/hw/pci/pci_bridge.c
> index 7eab9d5..6c35171 100644
> --- a/hw/pci/pci_bridge.c
> +++ b/hw/pci/pci_bridge.c
> @@ -269,7 +269,10 @@ void pci_bridge_write_config(PCIDevice *d,
>      newctl = pci_get_word(d->config + PCI_BRIDGE_CONTROL);
>      if (~oldctl & newctl & PCI_BRIDGE_CTL_BUS_RESET) {
>          /* Trigger hot reset on 0->1 transition. */
> -        qbus_reset_all(&s->sec_bus.qbus);
> +        qbus_walk_children(&s->sec_bus.qbus, NULL,
> +                           pcibus_pre_reset,
> +                           qdev_reset_one,
> +                           qbus_reset_one, &s->sec_bus.qbus);
>      }
>  }
>  
> diff --git a/include/hw/pci/pci_bus.h b/include/hw/pci/pci_bus.h
> index 7812fa9..9dd2d6c 100644
> --- a/include/hw/pci/pci_bus.h
> +++ b/include/hw/pci/pci_bus.h
> @@ -40,11 +40,15 @@ struct PCIBus {
>      int nirq;
>      int *irq_count;
>  
> +    bool bus_in_reset;
> +    uint32_t reset_seqid;
> +
>      NotifierWithReturnList hotplug_notifiers;
>  };
>  
>  void pci_bus_add_hotplug_notifier(PCIBus *bus, NotifierWithReturn *notify);
>  void pci_bus_remove_hotplug_notifier(NotifierWithReturn *notify);
> +int pcibus_pre_reset(BusState *qbus, void *opaque);
>  
>  typedef struct PCIBridgeWindows PCIBridgeWindows;
>  
> diff --git a/include/hw/qdev-core.h b/include/hw/qdev-core.h
> index abcdee8..3d71c17 100644
> --- a/include/hw/qdev-core.h
> +++ b/include/hw/qdev-core.h
> @@ -401,4 +401,7 @@ static inline bool qbus_is_hotpluggable(BusState *bus)
>  void device_listener_register(DeviceListener *listener);
>  void device_listener_unregister(DeviceListener *listener);
>  
> +int qdev_reset_one(DeviceState *dev, void *opaque);
> +int qbus_reset_one(BusState *bus, void *opaque);
> +
>  #endif
> -- 
> 1.9.3
> 
>