virtio: Introduce virtio_add_queue_aio

Using this function instead of virtio_add_queue marks the vq as aio
based. This differentiation will be useful in later patches.

Distinguish between virtqueue processing in the iohandler context and main loop
AioContext.  iohandler context is isolated from AioContexts and therefore does
not run during aio_poll().
Signed-off-by: NFam Zheng <famz@redhat.com>
Reviewed-by: NMichael S. Tsirkin <mst@redhat.com>
Signed-off-by: NMichael S. Tsirkin <mst@redhat.com>
Reviewed-by: NCornelia Huck <cornelia.huck@de.ibm.com>
Reviewed-by: NStefan Hajnoczi <stefanha@redhat.com>
Acked-by: NPaolo Bonzini <pbonzini@redhat.com>

hw/virtio/virtio.c

@@ -97,6 +97,7 @@ struct VirtQueue
     uint16_t vector;
     VirtIOHandleOutput handle_output;
     VirtIOHandleOutput handle_aio_output;
+    bool use_aio;
     VirtIODevice *vdev;
     EventNotifier guest_notifier;
     EventNotifier host_notifier;
@@ -1130,8 +1131,9 @@ void virtio_queue_set_vector(VirtIODevice *vdev, int n, uint16_t vector)
     }
 }
 
-VirtQueue *virtio_add_queue(VirtIODevice *vdev, int queue_size,
-                            VirtIOHandleOutput handle_output)
+static VirtQueue *virtio_add_queue_internal(VirtIODevice *vdev, int queue_size,
+                                            VirtIOHandleOutput handle_output,
+                                            bool use_aio)
 {
     int i;
 
@@ -1148,10 +1150,28 @@ VirtQueue *virtio_add_queue(VirtIODevice *vdev, int queue_size,
     vdev->vq[i].vring.align = VIRTIO_PCI_VRING_ALIGN;
     vdev->vq[i].handle_output = handle_output;
     vdev->vq[i].handle_aio_output = NULL;
+    vdev->vq[i].use_aio = use_aio;
 
     return &vdev->vq[i];
 }
 
+/* Add a virt queue and mark AIO.
+ * An AIO queue will use the AioContext based event interface instead of the
+ * default IOHandler and EventNotifier interface.
+ */
+VirtQueue *virtio_add_queue_aio(VirtIODevice *vdev, int queue_size,
+                                VirtIOHandleOutput handle_output)
+{
+    return virtio_add_queue_internal(vdev, queue_size, handle_output, true);
+}
+
+/* Add a normal virt queue (on the contrary to the AIO version above. */
+VirtQueue *virtio_add_queue(VirtIODevice *vdev, int queue_size,
+                            VirtIOHandleOutput handle_output)
+{
+    return virtio_add_queue_internal(vdev, queue_size, handle_output, false);
+}
+
 void virtio_del_queue(VirtIODevice *vdev, int n)
 {
     if (n < 0 || n >= VIRTIO_QUEUE_MAX) {
@@ -1830,11 +1850,21 @@ static void virtio_queue_host_notifier_read(EventNotifier *n)
 void virtio_queue_set_host_notifier_fd_handler(VirtQueue *vq, bool assign,
                                                bool set_handler)
 {
+    AioContext *ctx = qemu_get_aio_context();
     if (assign && set_handler) {
-        event_notifier_set_handler(&vq->host_notifier, true,
+        if (vq->use_aio) {
+            aio_set_event_notifier(ctx, &vq->host_notifier, true,
                                    virtio_queue_host_notifier_read);
+        } else {
+            event_notifier_set_handler(&vq->host_notifier, true,
+                                       virtio_queue_host_notifier_read);
+        }
     } else {
-        event_notifier_set_handler(&vq->host_notifier, true, NULL);
+        if (vq->use_aio) {
+            aio_set_event_notifier(ctx, &vq->host_notifier, true, NULL);
+        } else {
+            event_notifier_set_handler(&vq->host_notifier, true, NULL);
+        }
     }
     if (!assign) {
         /* Test and clear notifier before after disabling event,

include/hw/virtio/virtio.h

@@ -143,6 +143,9 @@ typedef void (*VirtIOHandleOutput)(VirtIODevice *, VirtQueue *);
 VirtQueue *virtio_add_queue(VirtIODevice *vdev, int queue_size,
                             VirtIOHandleOutput handle_output);
 
+VirtQueue *virtio_add_queue_aio(VirtIODevice *vdev, int queue_size,
+                                VirtIOHandleOutput handle_output);
+
 void virtio_del_queue(VirtIODevice *vdev, int n);
 
 void *virtqueue_alloc_element(size_t sz, unsigned out_num, unsigned in_num);