ixgbevf: Fix statistics corruption

When the physical function (PF) is reset for any reason the statistics
collection in ixgbevf_update_stats needs to wait to update until after
the reset synchronization ensures that the PF driver is up and running
and is finished with its own reset.  Go ahead and clear the link flag to
indicate this when the control message from the PF is received.  The
reset synchronization and recovery in the watchdog task will eventually
set the link flag up when the PF has resumed.
Signed-off-by: Greg Rose <gregory.v.rose@intel.com>
Tested-by: Sibai Li <sibai.li@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>

drivers/net/ethernet/intel/ixgbevf/ixgbevf_main.c

@@ -762,9 +762,11 @@ static irqreturn_t ixgbevf_msix_other(int irq, void *data)
 	if (!hw->mbx.ops.check_for_msg(hw)) {
 		hw->mbx.ops.read(hw, &msg, 1);
 
-		if ((msg & IXGBE_MBVFICR_VFREQ_MASK) == IXGBE_PF_CONTROL_MSG)
+		if ((msg & IXGBE_MBVFICR_VFREQ_MASK) == IXGBE_PF_CONTROL_MSG) {
 			mod_timer(&adapter->watchdog_timer,
 				  round_jiffies(jiffies + 1));
+			adapter->link_up = false;
+		}
 
 		if (msg & IXGBE_VT_MSGTYPE_NACK)
 			dev_info(&pdev->dev,
@@ -2118,6 +2120,9 @@ void ixgbevf_update_stats(struct ixgbevf_adapter *adapter)
 	struct ixgbe_hw *hw = &adapter->hw;
 	int i;
 
+	if (!adapter->link_up)
+		return;
+
 	UPDATE_VF_COUNTER_32bit(IXGBE_VFGPRC, adapter->stats.last_vfgprc,
 				adapter->stats.vfgprc);
 	UPDATE_VF_COUNTER_32bit(IXGBE_VFGPTC, adapter->stats.last_vfgptc,