virtio-bus: common ioeventfd infrastructure

Introduce a set of ioeventfd callbacks on the virtio-bus level
that can be implemented by the individual transports. At the
virtio-bus level, do common handling for host notifiers (which
is actually most of it).

Two things of note:
- When setting the host notifier, we only switch from/to the
  generic ioeventfd handler. This fixes a latent bug where we
  had no ioeventfd assigned for a certain window.
- We always iterate over all possible virtio queues, even though
  ccw (currently) has a lower limit. It does not really matter
  here.

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

1 files changed, 30 insertions, 0 deletions

diff --git a/include/hw/virtio/virtio-bus.h b/include/hw/virtio/virtio-bus.h
index 3f2c1363d0..9637f80f4d 100644
--- a/include/hw/virtio/virtio-bus.h
+++ b/include/hw/virtio/virtio-bus.h
@@ -71,6 +71,29 @@ typedef struct VirtioBusClass {
     void (*device_unplugged)(DeviceState *d);
     int (*query_nvectors)(DeviceState *d);
     /*
+     * ioeventfd handling: if the transport implements ioeventfd_started,
+     * it must implement the other ioeventfd callbacks as well
+     */
+    /* Returns true if the ioeventfd has been started for the device. */
+    bool (*ioeventfd_started)(DeviceState *d);
+    /*
+     * Sets the 'ioeventfd started' state after the ioeventfd has been
+     * started/stopped for the device. err signifies whether an error
+     * had occurred.
+     */
+    void (*ioeventfd_set_started)(DeviceState *d, bool started, bool err);
+    /* Returns true if the ioeventfd has been disabled for the device. */
+    bool (*ioeventfd_disabled)(DeviceState *d);
+    /* Sets the 'ioeventfd disabled' state for the device. */
+    void (*ioeventfd_set_disabled)(DeviceState *d, bool disabled);
+    /*
+     * Assigns/deassigns the ioeventfd backing for the transport on
+     * the device for queue number n. Returns an error value on
+     * failure.
+     */
+    int (*ioeventfd_assign)(DeviceState *d, EventNotifier *notifier,
+                            int n, bool assign);
+    /*
      * Does the transport have variable vring alignment?
      * (ie can it ever call virtio_queue_set_align()?)
      * Note that changing this will break migration for this transport.
@@ -111,4 +134,11 @@ static inline VirtIODevice *virtio_bus_get_device(VirtioBusState *bus)
     return (VirtIODevice *)qdev;
 }
 
+/* Start the ioeventfd. */
+void virtio_bus_start_ioeventfd(VirtioBusState *bus);
+/* Stop the ioeventfd. */
+void virtio_bus_stop_ioeventfd(VirtioBusState *bus);
+/* Switch from/to the generic ioeventfd handler */
+int virtio_bus_set_host_notifier(VirtioBusState *bus, int n, bool assign);
+
 #endif /* VIRTIO_BUS_H */