Re: [PATCH] virtio_rpmsg: set DRIVER_OK before using device
From: Michael S. Tsirkin
Date: Mon Mar 09 2015 - 04:41:18 EST
On Sat, Mar 07, 2015 at 08:06:56PM +0100, Michael S. Tsirkin wrote:
> 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
> Signed-off-by: Michael S. Tsirkin <mst@xxxxxxxxxx>
Ohad, can you review and ack pls?
> Note: compile-tested only.
> drivers/rpmsg/virtio_rpmsg_bus.c | 17 ++++++++++++++++-
> 1 file changed, 16 insertions(+), 1 deletion(-)
> diff --git a/drivers/rpmsg/virtio_rpmsg_bus.c b/drivers/rpmsg/virtio_rpmsg_bus.c
> index 92f6af6..73354ee 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");
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