ibmvnic: improve failover sysfs entry

The current implementation relies on H_IOCTL call to issue a
H_SESSION_ERR_DETECTED command to let the hypervisor to send a failover
signal. However, it may not work if there is no backup device or if
the vnic is already in error state,
e.g., "ibmvnic 30000003 env3: rx buffer returned with rc 6".
Add a last resort, that is to schedule a failover reset via CRQ command.

Signed-off-by: Lijun Pan <lijunp213@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/ibm/ibmvnic.c

@@ -5503,23 +5503,25 @@ static ssize_t failover_store(struct device *dev, struct device_attribute *attr,
 	if (rc) {
 		netdev_err(netdev, "Couldn't retrieve session token, rc %ld\n",
 			   rc);
-		return -EINVAL;
+		goto last_resort;
 	}
 
 	session_token = (__be64)retbuf[0];
 	netdev_dbg(netdev, "Initiating client failover, session id %llx\n",
 		   be64_to_cpu(session_token));
 	rc = plpar_hcall_norets(H_VIOCTL, adapter->vdev->unit_address,
 				H_SESSION_ERR_DETECTED, session_token, 0, 0);
-	if (rc) {
-		netdev_err(netdev, "Client initiated failover failed, rc %ld\n",
+	if (rc)
+		netdev_err(netdev,
+			   "H_VIOCTL initiated failover failed, rc %ld\n",
 			   rc);
-		return -EINVAL;
-	}
+
+last_resort:
+	netdev_dbg(netdev, "Trying to send CRQ_CMD, the last resort\n");
+	ibmvnic_reset(adapter, VNIC_RESET_FAILOVER);
 
 	return count;
 }
-
 static DEVICE_ATTR_WO(failover);
 
 static unsigned long ibmvnic_get_desired_dma(struct vio_dev *vdev)