virtio: introduce virtio_device_ioeventfd_enabled

This will be used to forbid iothread configuration when the
proxy does not allow using ioeventfd.  To simplify the implementation,
change the direction of the ioeventfd_disabled callback too.

Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

1 files changed, 9 insertions, 1 deletions

diff --git a/hw/virtio/virtio-bus.c b/hw/virtio/virtio-bus.c
index a8d2bd89c5..3ffec66d59 100644
--- a/hw/virtio/virtio-bus.c
+++ b/hw/virtio/virtio-bus.c
@@ -193,7 +193,7 @@ int virtio_bus_start_ioeventfd(VirtioBusState *bus)
     VirtioDeviceClass *vdc = VIRTIO_DEVICE_GET_CLASS(vdev);
     int r;
 
-    if (!k->ioeventfd_assign || k->ioeventfd_disabled(proxy)) {
+    if (!k->ioeventfd_assign || !k->ioeventfd_enabled(proxy)) {
         return -ENOSYS;
     }
     if (bus->ioeventfd_started || bus->ioeventfd_disabled) {
@@ -223,6 +223,14 @@ void virtio_bus_stop_ioeventfd(VirtioBusState *bus)
     bus->ioeventfd_started = false;
 }
 
+bool virtio_bus_ioeventfd_enabled(VirtioBusState *bus)
+{
+    VirtioBusClass *k = VIRTIO_BUS_GET_CLASS(bus);
+    DeviceState *proxy = DEVICE(BUS(bus)->parent);
+
+    return k->ioeventfd_assign && k->ioeventfd_enabled(proxy);
+}
+
 /*
  * This function switches from/to the generic ioeventfd handler.
  * assign==false means 'use generic ioeventfd handler'.