net/mlx4_core: Use msi_x module param to limit num of MSI-X irqs

Extend the boolean interpretation of msi_x module parameter
to numerical, as follows:

0   - Don't use MSI-X.
1   - Use MSI-X, driver decides the num of MSI-X irqs.
>=2 - Use MSI-X, limit number of MSI-X irqs to msi_x.
      In SRIOV, this limits the number of MSI-X irqs per VF.

Signed-off-by: Tariq Toukan <tariqt@mellanox.com>
Cc: Ajaykumar Hotchandani <ajaykumar.hotchandani@oracle.com>
Reviewed-by: Ajaykumar Hotchandani <ajaykumar.hotchandani@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/mellanox/mlx4/main.c

@@ -73,7 +73,7 @@ MODULE_PARM_DESC(debug_level, "Enable debug tracing if > 0");
 
 static int msi_x = 1;
 module_param(msi_x, int, 0444);
-MODULE_PARM_DESC(msi_x, "attempt to use MSI-X if nonzero");
+MODULE_PARM_DESC(msi_x, "0 - don't use MSI-X, 1 - use MSI-X, >1 - limit number of MSI-X irqs to msi_x");
 
 #else /* CONFIG_PCI_MSI */
 
@@ -2815,6 +2815,9 @@ static void mlx4_enable_msi_x(struct mlx4_dev *dev)
 				dev->caps.num_eqs - dev->caps.reserved_eqs,
 				MAX_MSIX);
 
+		if (msi_x > 1)
+			nreq = min_t(int, nreq, msi_x);
+
 		entries = kcalloc(nreq, sizeof(*entries), GFP_KERNEL);
 		if (!entries)
 			goto no_msi;
@@ -4182,6 +4185,11 @@ static struct pci_driver mlx4_driver = {
 
 static int __init mlx4_verify_params(void)
 {
+	if (msi_x < 0) {
+		pr_warn("mlx4_core: bad msi_x: %d\n", msi_x);
+		return -1;
+	}
+
 	if ((log_num_mac < 0) || (log_num_mac > 7)) {
 		pr_warn("mlx4_core: bad num_mac: %d\n", log_num_mac);
 		return -1;