From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>

Register the UFD that comes in as the response to the 'advise' method
with the postcopy code.

Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
---
 hw/virtio/vhost-user.c | 20 +++++++++++++++++++-
 1 file changed, 19 insertions(+), 1 deletion(-)

diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c
index ceb17b0554..5900583437 100644
--- a/hw/virtio/vhost-user.c
+++ b/hw/virtio/vhost-user.c
@@ -171,6 +171,7 @@ struct vhost_user {
     CharBackend *chr;
     int slave_fd;
     NotifierWithReturn postcopy_notifier;
+    struct PostCopyFD  postcopy_fd;
 };
 
 static bool ioeventfd_enabled(void)
@@ -796,6 +797,17 @@ out:
     return ret;
 }
 
+/*
+ * Called back from the postcopy fault thread when a fault is received on our
+ * ufd.
+ * TODO: This is Linux specific
+ */
+static int vhost_user_postcopy_fault_handler(struct PostCopyFD *pcfd,
+                                             void *ufd)
+{
+    return 0;
+}
+
 /*
  * Called at the start of an inbound postcopy on reception of the
  * 'advise' command.
@@ -835,8 +847,14 @@ static int vhost_user_postcopy_advise(struct vhost_dev *dev, Error **errp)
         error_setg(errp, "%s: Failed to get ufd", __func__);
         return -1;
     }
+    fcntl(ufd, F_SETFL, O_NONBLOCK);
 
-    /* TODO: register ufd with userfault thread */
+    /* register ufd with userfault thread */
+    u->postcopy_fd.fd = ufd;
+    u->postcopy_fd.data = dev;
+    u->postcopy_fd.handler = vhost_user_postcopy_fault_handler;
+    u->postcopy_fd.idstr = "vhost-user"; /* Need to find unique name */
+    postcopy_register_shared_ufd(&u->postcopy_fd);
     return 0;
 }
 
-- 
2.14.3