Merge tag 'vfio-v3.11-rc4' of git://github.com/awilliam/linux-vfio

torvalds · torvalds · commit 3df765fc6535 · 2013-07-31T17:53:38.000-07:00
Pull vfio fixes from Alex Williamson:
 "misc fixes around overreacting to bus notifier events and a locking
  fix for a corner case blocked remove"

* tag 'vfio-v3.11-rc4' of git://github.com/awilliam/linux-vfio:
  vfio-pci: Avoid deadlock on remove
  vfio: Ignore sprurious notifies
  vfio: Don't overreact to DEL_DEVICE
diff --git a/drivers/vfio/pci/vfio_pci.c b/drivers/vfio/pci/vfio_pci.c
@@ -137,8 +137,27 @@ static void vfio_pci_disable(struct vfio_pci_device *vdev)
 	 */
 	pci_write_config_word(pdev, PCI_COMMAND, PCI_COMMAND_INTX_DISABLE);
 
-	if (vdev->reset_works)
-		__pci_reset_function(pdev);
+	/*
+	 * Careful, device_lock may already be held.  This is the case if
+	 * a driver unbind is blocked.  Try to get the locks ourselves to
+	 * prevent a deadlock.
+	 */
+	if (vdev->reset_works) {
+		bool reset_done = false;
+
+		if (pci_cfg_access_trylock(pdev)) {
+			if (device_trylock(&pdev->dev)) {
+				__pci_reset_function_locked(pdev);
+				reset_done = true;
+				device_unlock(&pdev->dev);
+			}
+			pci_cfg_access_unlock(pdev);
+		}
+
+		if (!reset_done)
+			pr_warn("%s: Unable to acquire locks for reset of %s\n",
+				__func__, dev_name(&pdev->dev));
+	}
 
 	pci_restore_state(pdev);
 }
diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c
@@ -494,27 +494,6 @@ static int vfio_group_nb_add_dev(struct vfio_group *group, struct device *dev)
 	return 0;
 }
 
-static int vfio_group_nb_del_dev(struct vfio_group *group, struct device *dev)
-{
-	struct vfio_device *device;
-
-	/*
-	 * Expect to fall out here.  If a device was in use, it would
-	 * have been bound to a vfio sub-driver, which would have blocked
-	 * in .remove at vfio_del_group_dev.  Sanity check that we no
-	 * longer track the device, so it's safe to remove.
-	 */
-	device = vfio_group_get_device(group, dev);
-	if (likely(!device))
-		return 0;
-
-	WARN("Device %s removed from live group %d!\n", dev_name(dev),
-	     iommu_group_id(group->iommu_group));
-
-	vfio_device_put(device);
-	return 0;
-}
-
 static int vfio_group_nb_verify(struct vfio_group *group, struct device *dev)
 {
 	/* We don't care what happens when the group isn't in use */
@@ -531,21 +510,25 @@ static int vfio_iommu_group_notifier(struct notifier_block *nb,
 	struct device *dev = data;
 
 	/*
-	 * Need to go through a group_lock lookup to get a reference or
-	 * we risk racing a group being removed.  Leave a WARN_ON for
-	 * debuging, but if the group no longer exists, a spurious notify
-	 * is harmless.
+	 * Need to go through a group_lock lookup to get a reference or we
+	 * risk racing a group being removed.  Ignore spurious notifies.
 	 */
 	group = vfio_group_try_get(group);
-	if (WARN_ON(!group))
+	if (!group)
 		return NOTIFY_OK;
 
 	switch (action) {
 	case IOMMU_GROUP_NOTIFY_ADD_DEVICE:
 		vfio_group_nb_add_dev(group, dev);
 		break;
 	case IOMMU_GROUP_NOTIFY_DEL_DEVICE:
-		vfio_group_nb_del_dev(group, dev);
+		/*
+		 * Nothing to do here.  If the device is in use, then the
+		 * vfio sub-driver should block the remove callback until
+		 * it is unused.  If the device is unused or attached to a
+		 * stub driver, then it should be released and we don't
+		 * care that it will be going away.
+		 */
 		break;
 	case IOMMU_GROUP_NOTIFY_BIND_DRIVER:
 		pr_debug("%s: Device %s, group %d binding to driver\n",
