On Mon, Oct 06, 2014 at 01:33:38PM +0200, Cornelia Huck wrote:

On Sun, 5 Oct 2014 19:07:05 +0300
"Michael S. Tsirkin" [off-list ref] wrote:

quoted

Defer config changed notifications that arrive during
probe/scan/freeze/restore.

This will allow drivers to set DRIVER_OK earlier, without worrying about
racing with config change interrupts.

This change will also benefit old hypervisors (before 2009)
that send interrupts without checking DRIVER_OK: previously,
the callback could race with driver-specific initialization.

This will also help simplify drivers.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
---
 include/linux/virtio.h  |  6 ++++++
 drivers/virtio/virtio.c | 55 +++++++++++++++++++++++++++++++++++++++++--------
 2 files changed, 52 insertions(+), 9 deletions(-)

diff --git a/drivers/virtio/virtio.c b/drivers/virtio/virtio.c
index 657f817..578e02d 100644
--- a/drivers/virtio/virtio.c
+++ b/drivers/virtio/virtio.c

@@ -117,6 +117,40 @@ void virtio_check_driver_offered_feature(const struct virtio_device *vdev,
 }
 EXPORT_SYMBOL_GPL(virtio_check_driver_offered_feature);

+static void __virtio_config_changed(struct virtio_device *dev)
+{
+	struct virtio_driver *drv = drv_to_virtio(dev->dev.driver);
+
+	if (!dev->config_enabled)
+		dev->config_changed = true;
+	else if (drv && drv->config_changed)
+		drv->config_changed(dev);
+}
+
+void virtio_config_changed(struct virtio_device *dev)
+{
+	spin_lock_irq(&dev->config_lock);
+	__virtio_config_changed(dev);
+	spin_unlock_irq(&dev->config_lock);

Hm, isn't this function called from the interrupt handler?

Good catch, will fix up, thanks!
 

quoted

+}
+EXPORT_SYMBOL_GPL(virtio_config_changed);
+
+static void virtio_config_disable(struct virtio_device *dev)
+{
+	spin_lock_irq(&dev->config_lock);
+	dev->config_enabled = false;
+	spin_unlock_irq(&dev->config_lock);
+}
+
+static void virtio_config_enable(struct virtio_device *dev)
+{
+	spin_lock_irq(&dev->config_lock);
+	dev->config_enabled = true;
+	__virtio_config_changed(dev);
+	dev->config_changed = false;
+	spin_unlock_irq(&dev->config_lock);
+}
+

Maybe call these virtio_config_change_{dis,en}able()?

quoted

 static int virtio_dev_probe(struct device *_d)
 {
 	int err, i;