/* On success, ioeventfd ownership belongs to the caller. */
int virtio_bus_grab_ioeventfd(VirtioBusState *bus)
{
VirtioBusClass *k = VIRTIO_BUS_GET_CLASS(bus);
/* vhost can be used even if ioeventfd=off in the proxy device,
* so do not check k->ioeventfd_enabled.
*/
if (!k->ioeventfd_assign) {
return -ENOSYS;
}
if (bus->ioeventfd_grabbed == 0 && bus->ioeventfd_started) {
virtio_bus_stop_ioeventfd(bus);
/* Remember that we need to restart ioeventfd
* when ioeventfd_grabbed becomes zero.
*/
bus->ioeventfd_started = true;
}
bus->ioeventfd_grabbed++;
return 0;
}
/*
* This function switches from/to the generic ioeventfd handler.
* assign==false means 'use generic ioeventfd handler'.
*/
int virtio_bus_set_host_notifier(VirtioBusState *bus, int n, bool assign)
{
VirtioBusClass *k = VIRTIO_BUS_GET_CLASS(bus);
DeviceState *proxy = DEVICE(BUS(bus)->parent);
if (!k->ioeventfd_started) {
return -ENOSYS;
}
k->ioeventfd_set_disabled(proxy, assign);
if (assign) {
/*
* Stop using the generic ioeventfd, we are doing eventfd handling
* ourselves below
*
* FIXME: We should just switch the handler and not deassign the
* ioeventfd.
* Otherwise, there's a window where we don't have an
* ioeventfd and we may end up with a notification where
* we don't expect one.
*/
virtio_bus_stop_ioeventfd(bus);
}
return set_host_notifier_internal(proxy, bus, n, assign, false);
}
static void virtio_mmio_stop_ioeventfd(VirtIOMMIOProxy *proxy)
{
virtio_bus_stop_ioeventfd(&proxy->bus);
}