iavf: Fix locking for VIRTCHNL_OP_GET_OFFLOAD_VLAN_V2_CAPS

iavf_virtchnl_completion is called under crit_lock but when
the code for VIRTCHNL_OP_GET_OFFLOAD_VLAN_V2_CAPS is called,
this lock is released in order to obtain rtnl_lock to avoid
ABBA deadlock with unregister_netdev.

Along with the new way iavf_remove behaves, there exist
many risks related to the lock release and attmepts to regrab
it. The driver faces crashes related to races between
unregister_netdev and netdev_update_features. Yet another
risk is that the driver could already obtain the crit_lock
in order to destroy it and iavf_virtchnl_completion could
crash or block forever.

Make iavf_virtchnl_completion never relock crit_lock in it's
call paths.

Extract rtnl_lock locking logic to the driver for
unregister_netdev in order to set the netdev_registered flag
inside the lock.

Introduce a new flag that will inform adminq_task to perform
the code from VIRTCHNL_OP_GET_OFFLOAD_VLAN_V2_CAPS right after
it finishes processing messages. Guard this code with remove
flags so it's never called when the driver is in remove state.

Fixes: 5951a2b9 ("iavf: Fix VLAN feature flags after VFR")
Signed-off-by: Slawomir Laba <slawomirx.laba@intel.com>
Signed-off-by: Phani Burra <phani.r.burra@intel.com>
Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
Signed-off-by: Mateusz Palczewski <mateusz.palczewski@intel.com>
Tested-by: Konrad Jankowski <konrad0.jankowski@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>

drivers/net/ethernet/intel/iavf/iavf.h

@@ -287,6 +287,7 @@ struct iavf_adapter {
 #define IAVF_FLAG_LEGACY_RX			BIT(15)
 #define IAVF_FLAG_REINIT_ITR_NEEDED		BIT(16)
 #define IAVF_FLAG_QUEUES_DISABLED		BIT(17)
+#define IAVF_FLAG_SETUP_NETDEV_FEATURES		BIT(18)
 /* duplicates for common code */
 #define IAVF_FLAG_DCB_ENABLED			0
 	/* flags for admin queue service task */

drivers/net/ethernet/intel/iavf/iavf_main.c

@@ -2879,6 +2879,24 @@ static void iavf_adminq_task(struct work_struct *work)
 	} while (pending);
 	mutex_unlock(&adapter->crit_lock);
 
+	if ((adapter->flags & IAVF_FLAG_SETUP_NETDEV_FEATURES)) {
+		if (adapter->netdev_registered ||
+		    !test_bit(__IAVF_IN_REMOVE_TASK, &adapter->crit_section)) {
+			struct net_device *netdev = adapter->netdev;
+
+			rtnl_lock();
+			netdev_update_features(netdev);
+			rtnl_unlock();
+			/* Request VLAN offload settings */
+			if (VLAN_V2_ALLOWED(adapter))
+				iavf_set_vlan_offload_features
+					(adapter, 0, netdev->features);
+
+			iavf_set_queue_vlan_tag_loc(adapter);
+		}
+
+		adapter->flags &= ~IAVF_FLAG_SETUP_NETDEV_FEATURES;
+	}
 	if ((adapter->flags &
 	     (IAVF_FLAG_RESET_PENDING | IAVF_FLAG_RESET_NEEDED)) ||
 	    adapter->state == __IAVF_RESETTING)
@@ -4606,8 +4624,10 @@ static void iavf_remove(struct pci_dev *pdev)
 	cancel_delayed_work_sync(&adapter->watchdog_task);
 
 	if (adapter->netdev_registered) {
-		unregister_netdev(netdev);
+		rtnl_lock();
+		unregister_netdevice(netdev);
 		adapter->netdev_registered = false;
+		rtnl_unlock();
 	}
 	if (CLIENT_ALLOWED(adapter)) {
 		err = iavf_lan_del_device(adapter);

drivers/net/ethernet/intel/iavf/iavf_virtchnl.c

@@ -2146,29 +2146,7 @@ void iavf_virtchnl_completion(struct iavf_adapter *adapter,
 				     sizeof(adapter->vlan_v2_caps)));
 
 		iavf_process_config(adapter);
-
-		/* unlock crit_lock before acquiring rtnl_lock as other
-		 * processes holding rtnl_lock could be waiting for the same
-		 * crit_lock
-		 */
-		mutex_unlock(&adapter->crit_lock);
-		/* VLAN capabilities can change during VFR, so make sure to
-		 * update the netdev features with the new capabilities
-		 */
-		rtnl_lock();
-		netdev_update_features(netdev);
-		rtnl_unlock();
-		if (iavf_lock_timeout(&adapter->crit_lock, 10000))
-			dev_warn(&adapter->pdev->dev, "failed to acquire crit_lock in %s\n",
-				 __FUNCTION__);
-
-		/* Request VLAN offload settings */
-		if (VLAN_V2_ALLOWED(adapter))
-			iavf_set_vlan_offload_features(adapter, 0,
-						       netdev->features);
-
-		iavf_set_queue_vlan_tag_loc(adapter);
-
+		adapter->flags |= IAVF_FLAG_SETUP_NETDEV_FEATURES;
 		}
 		break;
 	case VIRTCHNL_OP_ENABLE_QUEUES: