ixgbe: don't check minimum link when direct assigned to virtual machine

This patch prevents the display of the minimum link qualification check
if we might be in a virtual machine. This check is incorrect and
misleading in this case, since we actually don't really know what the
available bandwidth is. To do so, we simply check whether each function
on the bus matches our device id. If it doesn't the most likely scenario
is that we're directly assigned to a virtual machine.

Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
Tested-by: Phil Schmitt <phillip.j.schmitt@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>

drivers/net/ethernet/intel/ixgbe/ixgbe_main.c

@@ -7973,7 +7973,7 @@ static const struct net_device_ops ixgbe_netdev_ops = {
  **/
 static inline int ixgbe_enumerate_functions(struct ixgbe_adapter *adapter)
 {
-	struct pci_dev *entry;
+	struct pci_dev *entry, *pdev = adapter->pdev;
 	int physfns = 0;
 
 	/* Some cards can not use the generic count PCIe functions method,
@@ -7985,8 +7985,20 @@ static inline int ixgbe_enumerate_functions(struct ixgbe_adapter *adapter)
 
 	list_for_each_entry(entry, &adapter->pdev->bus->devices, bus_list) {
 		/* don't count virtual functions */
-		if (!entry->is_virtfn)
-			physfns++;
+		if (entry->is_virtfn)
+			continue;
+
+		/* When the devices on the bus don't all match our device ID,
+		 * we can't reliably determine the correct number of
+		 * functions. This can occur if a function has been direct
+		 * attached to a virtual machine using VT-d, for example. In
+		 * this case, simply return -1 to indicate this.
+		 */
+		if ((entry->vendor != pdev->vendor) ||
+		    (entry->device != pdev->device))
+			return -1;
+
+		physfns++;
 	}
 
 	return physfns;
@@ -8381,7 +8393,10 @@ skip_sriov:
 		expected_gts = ixgbe_enumerate_functions(adapter) * 10;
 		break;
 	}
-	ixgbe_check_minimum_link(adapter, expected_gts);
+
+	/* don't check link if we failed to enumerate functions */
+	if (expected_gts > 0)
+		ixgbe_check_minimum_link(adapter, expected_gts);
 
 	err = ixgbe_read_pba_string_generic(hw, part_str, sizeof(part_str));
 	if (err)