3 files changed, 167 insertions, 20 deletions

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 95c97bec8018..b6d4afa8ba40 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -3250,6 +3250,18 @@ static void pci_dev_lock(struct pci_dev *dev)
         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);
@@ -3393,6 +3405,34 @@ int pci_reset_function(struct pci_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)
 {
@@ -3417,6 +3457,32 @@ static void pci_bus_unlock(struct pci_bus *bus)
         }
 }
 
+/* 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 */
 static void pci_slot_lock(struct pci_slot *slot)
 {
@@ -3445,6 +3511,37 @@ static void pci_slot_unlock(struct pci_slot *slot)
         }
 }
 
+/* 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 */
 static void pci_bus_save_and_disable(struct pci_bus *bus)
 {
@@ -3568,6 +3665,35 @@ int pci_reset_slot(struct pci_slot *slot)
 }
 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)
@@ -3627,6 +3753,35 @@ int pci_reset_bus(struct pci_bus *bus)
 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
  * @dev: PCI device to query
  *
diff --git a/drivers/vfio/pci/vfio_pci.c b/drivers/vfio/pci/vfio_pci.c
index 6ab71b9fcf8d..2319d206f630 100644
--- a/drivers/vfio/pci/vfio_pci.c
+++ b/drivers/vfio/pci/vfio_pci.c
@@ -139,25 +139,14 @@ static void vfio_pci_disable(struct vfio_pci_device *vdev)
         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);
@@ -514,7 +503,7 @@ static long vfio_pci_ioctl(void *device_data,
 
         } 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;
@@ -684,8 +673,8 @@ reset_info_exit:
                                                     &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--)
diff --git a/include/linux/pci.h b/include/linux/pci.h
index 2087e6b35545..fa959aac6169 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -949,10 +949,13 @@ int pcie_get_minimum_link(struct pci_dev *dev, enum pci_bus_speed *speed,
 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);