Re: [PATCH 0/2] irq: add get_gsi callback

Eric Auger
2015-04-23T11:20:04Z

Hi Paolo,

thanks for taking the time to explain. I will rewrite accordingly.

Best Regards

Eric

On 04/23/2015 11:58 AM, Paolo Bonzini wrote:
>
>
> On 23/04/2015 11:40, Eric Auger wrote:
>>>> Why can't you just use a GHashTable?
>> You mean implementing this hash table in the interrupt controller?
>
> No, in KVM. Basically the kvm-vgic interrupt controller registers its
> qemu_irqs with kvm-all.c, passing the gsi number for KVM_IRQFD along
> the way. Then VFIO device can pass the qemu_irq and ask for an irqfd
> for that qemu_irq, instead of having to know the gsi number. kvm-all.c
> acts as a mediator.
>
> The notifier actually is not even necessary, because we already have
> a very similar concept in QOM. But qdev_init_gpio_out_named always
> passes a dummy "notifier":
>
> void qdev_init_gpio_out_named(DeviceState *dev, qemu_irq *pins,
> const char *name, int n)
> {
> int i;
> NamedGPIOList *gpio_list = qdev_get_named_gpio_list(dev, name);
> char *propname = g_strdup_printf("%s[*]", name ? name : "unnamed-gpio-out");
>
> assert(gpio_list->num_in == 0 || !name);
> gpio_list->num_out += n;
>
> for (i = 0; i < n; ++i) {
> memset(&pins[i], 0, sizeof(*pins));
> object_property_add_link(OBJECT(dev), propname, TYPE_IRQ,
> (Object **)&pins[i],
> object_property_allow_set_link,
> OBJ_PROP_LINK_UNREF_ON_RELEASE,
> &error_abort);
> }
> g_free(propname);
> }
>
> So you need to add a method to DeviceClass, with the same prototype
> as object_property_allow_set_link, and set the default value to
> object_property_allow_set_link in device_class_init. Then
> qdev_init_gpio_out_named can do
>
> DeviceClass *dc = DEVICE_GET_CLASS(dev);
> ...
> object_property_add_link(OBJECT(dev), propname, TYPE_IRQ,
> (Object **)&pins[i],
> dc->gpio_set_hook,
> OBJ_PROP_LINK_UNREF_ON_RELEASE,
> &error_abort);
>
> or something like that.
>
> Alternatively, and probably better, add the argument to
> qdev_init_gpio_out_named; there aren't many calls. Then
> you can add the method only to SysbusDeviceClass rather than
> to all devices, and you can change sysbus_init_irq like this:
>
> void sysbus_init_irq(SysBusDevice *dev, qemu_irq *p)
> {
> SysBusDeviceClass *sdc = SYSBUS_DEVICE_GET_CLASS(dev);
> qdev_init_gpio_out_named(DEVICE(dev), p, SYSBUS_DEVICE_GPIO_IRQ, 1,
> sdc->irq_set_hook);
> }
>
>
> Paolo
>
>> The problem is my VFIO device currently has no link to the interrupt
>> controller object. Besides it has a platform bus in between. Previously
>> I devised a reset notifier called in the machine file to pass this link
>> but Alex was not keen about this method. So the idea here is when the
>> VFIO sysbus device qemuirq is getting connected, a notifier is called,
>> VFIO device can retrieve the gsi of this qemu_irq and call KVM_IRQFD
>> with that gsi.