Re: [Qemu-devel] [PATCH v2 2/2] pci: Add INTx routing notifier

[Jan Kiszka <jan.kiszka@siemens.com>]

On 2012-07-02 16:26, Alex Williamson wrote:
> On Mon, 2012-07-02 at 14:38 +0200, Jan Kiszka wrote:
>> This per-device notifier shall be triggered by any interrupt router
>> along the path of a device's legacy interrupt signal on routing changes.
>> For simplicity reasons and as this is a slow path anyway, no further
>> details on the routing changes are provided. Instead, the callback is
>> expected to use pci_device_route_intx_to_irq to check the effect of the
>> change.
>>
>> Will be used by KVM PCI device assignment and VFIO.
>>
>> Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
>> ---
>>  hw/pci.c      |   23 +++++++++++++++++++++++
>>  hw/pci.h      |    7 +++++++
>>  hw/piix_pci.c |    2 ++
>>  3 files changed, 32 insertions(+), 0 deletions(-)
>>
>> diff --git a/hw/pci.c b/hw/pci.c
>> index 311ba09..772141a 100644
>> --- a/hw/pci.c
>> +++ b/hw/pci.c
>> @@ -1095,6 +1095,29 @@ PCIINTxRoute pci_device_route_intx_to_irq(PCIDevice *dev, int pin)
>>      return bus->route_intx_to_irq(bus->irq_opaque, pin);
>>  }
>>  
>> +void pci_bus_fire_intx_routing_notifier(PCIBus *bus)
>> +{
>> +    PCIDevice *dev;
>> +    PCIBus *sec;
>> +    int i;
>> +
>> +    for (i = 0; i < ARRAY_SIZE(bus->devices); ++i) {
>> +        dev = bus->devices[i];
>> +        if (dev && dev->intx_routing_notifier) {
>> +            dev->intx_routing_notifier(dev);
>> +        }
>> +        QLIST_FOREACH(sec, &bus->child, sibling) {
>> +            pci_bus_fire_intx_routing_notifier(sec);
>> +        }
>> +    }
>> +}
>> +
>> +void pci_device_set_intx_routing_notifier(PCIDevice *dev,
>> +                                          PCIINTxRoutingNotifier notifier)
>> +{
>> +    dev->intx_routing_notifier = notifier;
>> +}
>> +
> 
> nit, wish there was also an unset here too.  If we switch to MSI mode,
> there's not much point in calling the notifier, so the driver could
> unset it.

We could add

static inline pci_device_unset_intx_routing_notifier(PCIDevice *dev)
{
    dev->intx_routing_notifier = NULL;
}

- or simply do pci_device_set_intx_routing_notifier(dev, NULL);.

>  Also nice to have a set in the initfn and matching unset in
> exitfn.  There's potentially a race between the driver freeing data and
> the pci device going away, but I don't know if we can hit it in qemu.

Everything should be synchronized by the BQL, so far. Or not?

Jan

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