virtio_rpmsg: set DRIVER_OK before using device

virtio spec requires that all drivers set DRIVER_OK
before using devices. While rpmsg isn't yet
included in the virtio 1 spec, previous spec versions
also required this.

virtio rpmsg violates this rule: is calls kick
before setting DRIVER_OK.

The fix isn't trivial since simply calling virtio_device_ready earlier
would mean we might get an interrupt in parallel with adding buffers.

Instead, split kick out to prepare+notify calls.  prepare before
virtio_device_ready - when we know we won't get interrupts. notify right
afterwards.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: Ohad Ben-Cohen <ohad@wizery.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

1 files changed, 16 insertions, 1 deletions

diff --git a/drivers/rpmsg/virtio_rpmsg_bus.c b/drivers/rpmsg/virtio_rpmsg_bus.c
index 92f6af6da699..73354ee27877 100644
--- a/drivers/rpmsg/virtio_rpmsg_bus.c
+++ b/drivers/rpmsg/virtio_rpmsg_bus.c
@@ -951,6 +951,7 @@ static int rpmsg_probe(struct virtio_device *vdev)
         void *bufs_va;
         int err = 0, i;
         size_t total_buf_space;
+        bool notify;
 
         vrp = kzalloc(sizeof(*vrp), GFP_KERNEL);
         if (!vrp)
@@ -1030,8 +1031,22 @@ static int rpmsg_probe(struct virtio_device *vdev)
                 }
         }
 
+        /*
+         * Prepare to kick but don't notify yet - we can't do this before
+         * device is ready.
+         */
+        notify = virtqueue_kick_prepare(vrp->rvq);
+
+        /* From this point on, we can notify and get callbacks. */
+        virtio_device_ready(vdev);
+
         /* tell the remote processor it can start sending messages */
-        virtqueue_kick(vrp->rvq);
+        /*
+         * this might be concurrent with callbacks, but we are only
+         * doing notify, not a full kick here, so that's ok.
+         */
+        if (notify)
+                virtqueue_notify(vrp->rvq);
 
         dev_info(&vdev->dev, "rpmsg host is online\n");