virtio: defer config changed notifications

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>
Reviewed-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> (cosmetic changes)

1 files changed, 49 insertions, 9 deletions

diff --git a/drivers/virtio/virtio.c b/drivers/virtio/virtio.c
index 8216b7311092..df598dd8c5c8 100644
--- a/drivers/virtio/virtio.c
+++ b/drivers/virtio/virtio.c
@@ -117,6 +117,43 @@ 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_change_pending = true;
+        else if (drv && drv->config_changed)
+                drv->config_changed(dev);
+}
+
+void virtio_config_changed(struct virtio_device *dev)
+{
+        unsigned long flags;
+
+        spin_lock_irqsave(&dev->config_lock, flags);
+        __virtio_config_changed(dev);
+        spin_unlock_irqrestore(&dev->config_lock, flags);
+}
+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;
+        if (dev->config_change_pending)
+                __virtio_config_changed(dev);
+        dev->config_change_pending = false;
+        spin_unlock_irq(&dev->config_lock);
+}
+
 static int virtio_dev_probe(struct device *_d)
 {
         int err, i;
@@ -153,6 +190,8 @@ static int virtio_dev_probe(struct device *_d)
                 add_status(dev, VIRTIO_CONFIG_S_DRIVER_OK);
                 if (drv->scan)
                         drv->scan(dev);
+
+                virtio_config_enable(dev);
         }
 
         return err;
@@ -163,6 +202,8 @@ static int virtio_dev_remove(struct device *_d)
         struct virtio_device *dev = dev_to_virtio(_d);
         struct virtio_driver *drv = drv_to_virtio(dev->dev.driver);
 
+        virtio_config_disable(dev);
+
         drv->remove(dev);
 
         /* Driver should have reset device. */
@@ -211,6 +252,10 @@ int register_virtio_device(struct virtio_device *dev)
         dev->index = err;
         dev_set_name(&dev->dev, "virtio%u", dev->index);
 
+        spin_lock_init(&dev->config_lock);
+        dev->config_enabled = false;
+        dev->config_change_pending = false;
+
         /* We always start by resetting the device, in case a previous
          * driver messed it up.  This also tests that code path a little. */
         dev->config->reset(dev);
@@ -239,20 +284,13 @@ void unregister_virtio_device(struct virtio_device *dev)
 }
 EXPORT_SYMBOL_GPL(unregister_virtio_device);
 
-void virtio_config_changed(struct virtio_device *dev)
-{
-        struct virtio_driver *drv = drv_to_virtio(dev->dev.driver);
-
-        if (drv && drv->config_changed)
-                drv->config_changed(dev);
-}
-EXPORT_SYMBOL_GPL(virtio_config_changed);
-
 #ifdef CONFIG_PM_SLEEP
 int virtio_device_freeze(struct virtio_device *dev)
 {
         struct virtio_driver *drv = drv_to_virtio(dev->dev.driver);
 
+        virtio_config_disable(dev);
+
         dev->failed = dev->config->get_status(dev) & VIRTIO_CONFIG_S_FAILED;
 
         if (drv && drv->freeze)
@@ -297,6 +335,8 @@ int virtio_device_restore(struct virtio_device *dev)
         /* Finally, tell the device we're all set */
         add_status(dev, VIRTIO_CONFIG_S_DRIVER_OK);
 
+        virtio_config_enable(dev);
+
         return 0;
 }
 EXPORT_SYMBOL_GPL(virtio_device_restore);