Merge branch 'pci/reset' into next

* pci/reset:
vfio-pci: Use pci "try" reset interface
PCI: Add pci_try_reset_function(), pci_try_reset_slot(), pci_try_reset_bus()

drivers/pci/pci.c

···
 	device_lock(&dev->dev);
 }
 
+/* Return 1 on successful lock, 0 on contention */
+static int pci_dev_trylock(struct pci_dev *dev)
+{
+	if (pci_cfg_access_trylock(dev)) {
+		if (device_trylock(&dev->dev))
+			return 1;
+		pci_cfg_access_unlock(dev);
+	}
+
+	return 0;
+}
+
 static void pci_dev_unlock(struct pci_dev *dev)
 {
 	device_unlock(&dev->dev);
···
 }
 EXPORT_SYMBOL_GPL(pci_reset_function);
 
+/**
+ * pci_try_reset_function - quiesce and reset a PCI device function
+ * @dev: PCI device to reset
+ *
+ * Same as above, except return -EAGAIN if unable to lock device.
+ */
+int pci_try_reset_function(struct pci_dev *dev)
+{
+	int rc;
+
+	rc = pci_dev_reset(dev, 1);
+	if (rc)
+		return rc;
+
+	pci_dev_save_and_disable(dev);
+
+	if (pci_dev_trylock(dev)) {
+		rc = __pci_dev_reset(dev, 0);
+		pci_dev_unlock(dev);
+	} else
+		rc = -EAGAIN;
+
+	pci_dev_restore(dev);
+
+	return rc;
+}
+EXPORT_SYMBOL_GPL(pci_try_reset_function);
+
 /* Lock devices from the top of the tree down */
 static void pci_bus_lock(struct pci_bus *bus)
 {
···
 			pci_bus_unlock(dev->subordinate);
 		pci_dev_unlock(dev);
 	}
+}
+
+/* Return 1 on successful lock, 0 on contention */
+static int pci_bus_trylock(struct pci_bus *bus)
+{
+	struct pci_dev *dev;
+
+	list_for_each_entry(dev, &bus->devices, bus_list) {
+		if (!pci_dev_trylock(dev))
+			goto unlock;
+		if (dev->subordinate) {
+			if (!pci_bus_trylock(dev->subordinate)) {
+				pci_dev_unlock(dev);
+				goto unlock;
+			}
+		}
+	}
+	return 1;
+
+unlock:
+	list_for_each_entry_continue_reverse(dev, &bus->devices, bus_list) {
+		if (dev->subordinate)
+			pci_bus_unlock(dev->subordinate);
+		pci_dev_unlock(dev);
+	}
+	return 0;
 }
 
 /* Lock devices from the top of the tree down */
···
 			pci_bus_unlock(dev->subordinate);
 		pci_dev_unlock(dev);
 	}
+}
+
+/* Return 1 on successful lock, 0 on contention */
+static int pci_slot_trylock(struct pci_slot *slot)
+{
+	struct pci_dev *dev;
+
+	list_for_each_entry(dev, &slot->bus->devices, bus_list) {
+		if (!dev->slot || dev->slot != slot)
+			continue;
+		if (!pci_dev_trylock(dev))
+			goto unlock;
+		if (dev->subordinate) {
+			if (!pci_bus_trylock(dev->subordinate)) {
+				pci_dev_unlock(dev);
+				goto unlock;
+			}
+		}
+	}
+	return 1;
+
+unlock:
+	list_for_each_entry_continue_reverse(dev,
+					     &slot->bus->devices, bus_list) {
+		if (!dev->slot || dev->slot != slot)
+			continue;
+		if (dev->subordinate)
+			pci_bus_unlock(dev->subordinate);
+		pci_dev_unlock(dev);
+	}
+	return 0;
 }
 
 /* Save and disable devices from the top of the tree down */
···
 }
 EXPORT_SYMBOL_GPL(pci_reset_slot);
 
+/**
+ * pci_try_reset_slot - Try to reset a PCI slot
+ * @slot: PCI slot to reset
+ *
+ * Same as above except return -EAGAIN if the slot cannot be locked
+ */
+int pci_try_reset_slot(struct pci_slot *slot)
+{
+	int rc;
+
+	rc = pci_slot_reset(slot, 1);
+	if (rc)
+		return rc;
+
+	pci_slot_save_and_disable(slot);
+
+	if (pci_slot_trylock(slot)) {
+		might_sleep();
+		rc = pci_reset_hotplug_slot(slot->hotplug, 0);
+		pci_slot_unlock(slot);
+	} else
+		rc = -EAGAIN;
+
+	pci_slot_restore(slot);
+
+	return rc;
+}
+EXPORT_SYMBOL_GPL(pci_try_reset_slot);
+
 static int pci_bus_reset(struct pci_bus *bus, int probe)
 {
 	if (!bus->self)
···
 	return rc;
 }
 EXPORT_SYMBOL_GPL(pci_reset_bus);
+
+/**
+ * pci_try_reset_bus - Try to reset a PCI bus
+ * @bus: top level PCI bus to reset
+ *
+ * Same as above except return -EAGAIN if the bus cannot be locked
+ */
+int pci_try_reset_bus(struct pci_bus *bus)
+{
+	int rc;
+
+	rc = pci_bus_reset(bus, 1);
+	if (rc)
+		return rc;
+
+	pci_bus_save_and_disable(bus);
+
+	if (pci_bus_trylock(bus)) {
+		might_sleep();
+		pci_reset_bridge_secondary_bus(bus->self);
+		pci_bus_unlock(bus);
+	} else
+		rc = -EAGAIN;
+
+	pci_bus_restore(bus);
+
+	return rc;
+}
+EXPORT_SYMBOL_GPL(pci_try_reset_bus);
 
 /**
  * pcix_get_max_mmrbc - get PCI-X maximum designed memory read byte count

drivers/vfio/pci/vfio_pci.c

···
 	pci_write_config_word(pdev, PCI_COMMAND, PCI_COMMAND_INTX_DISABLE);
 
 	/*
-	 * 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.
+	 * Try to reset the device.  The success of this is dependent on
+	 * being able to lock the device, which is not always possible.
 	 */
 	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));
+		int ret = pci_try_reset_function(pdev);
+		if (ret)
+			pr_warn("%s: Failed to reset device %s (%d)\n",
+				__func__, dev_name(&pdev->dev), ret);
 	}
 
 	pci_restore_state(pdev);
···
 
 	} else if (cmd == VFIO_DEVICE_RESET) {
 		return vdev->reset_works ?
-			pci_reset_function(vdev->pdev) : -EINVAL;
+			pci_try_reset_function(vdev->pdev) : -EINVAL;
 
 	} else if (cmd == VFIO_DEVICE_GET_PCI_HOT_RESET_INFO) {
 		struct vfio_pci_hot_reset_info hdr;
···
 						    &info, slot);
 		if (!ret)
 			/* User has access, do the reset */
-			ret = slot ? pci_reset_slot(vdev->pdev->slot) :
-				     pci_reset_bus(vdev->pdev->bus);
+			ret = slot ? pci_try_reset_slot(vdev->pdev->slot) :
+				     pci_try_reset_bus(vdev->pdev->bus);
 
 hot_reset_release:
 		for (i--; i >= 0; i--)

include/linux/pci.h

···
 int __pci_reset_function(struct pci_dev *dev);
 int __pci_reset_function_locked(struct pci_dev *dev);
 int pci_reset_function(struct pci_dev *dev);
+int pci_try_reset_function(struct pci_dev *dev);
 int pci_probe_reset_slot(struct pci_slot *slot);
 int pci_reset_slot(struct pci_slot *slot);
+int pci_try_reset_slot(struct pci_slot *slot);
 int pci_probe_reset_bus(struct pci_bus *bus);
 int pci_reset_bus(struct pci_bus *bus);
+int pci_try_reset_bus(struct pci_bus *bus);
 void pci_reset_bridge_secondary_bus(struct pci_dev *dev);
 void pci_update_resource(struct pci_dev *dev, int resno);
 int __must_check pci_assign_resource(struct pci_dev *dev, int i);