IB/mlx4: Fix EQ deallocation in legacy mode

Commit e605b743f3 ("IB/mlx4: Increase the number of vectors (EQs)
available for ULPs") didn't handle correctly the case where there
aren't enough MSI-X vectors to increase the number of EQs, so only the
legacy EQs are allocated.  This results in an attempt to memset() to
zero the EQ table which was never allocated and a kernel crash.

Fix this by checking in the teardown flow if the table of EQs was ever
allocated.  Also remove some unneeded setting to zero of the EQ
related fields in struct mlx4_ib_dev.

Signed-off-by: Shlomo Pongratz <shlomop@mellanox.com>
Signed-off-by: Or Gerlitz <ogerlitz@mellanox.com>
Signed-off-by: Roland Dreier <roland@purestorage.com>

drivers/infiniband/hw/mlx4/main.c

@@ -1084,12 +1084,9 @@ static void mlx4_ib_alloc_eqs(struct mlx4_dev *dev, struct mlx4_ib_dev *ibdev)
 	int total_eqs = 0;
 	int i, j, eq;
 
-	/* Init eq table */
-	ibdev->eq_table = NULL;
-	ibdev->eq_added = 0;
-
-	/* Legacy mode? */
-	if (dev->caps.comp_pool == 0)
+	/* Legacy mode or comp_pool is not large enough */
+	if (dev->caps.comp_pool == 0 ||
+	    dev->caps.num_ports > dev->caps.comp_pool)
 		return;
 
 	eq_per_port = rounddown_pow_of_two(dev->caps.comp_pool/
@@ -1135,7 +1132,10 @@ static void mlx4_ib_alloc_eqs(struct mlx4_dev *dev, struct mlx4_ib_dev *ibdev)
 static void mlx4_ib_free_eqs(struct mlx4_dev *dev, struct mlx4_ib_dev *ibdev)
 {
 	int i;
-	int total_eqs;
+
+	/* no additional eqs were added */
+	if (!ibdev->eq_table)
+		return;
 
 	/* Reset the advertised EQ number */
 	ibdev->ib_dev.num_comp_vectors = dev->caps.num_comp_vectors;
@@ -1148,12 +1148,7 @@ static void mlx4_ib_free_eqs(struct mlx4_dev *dev, struct mlx4_ib_dev *ibdev)
 		mlx4_release_eq(dev, ibdev->eq_table[i]);
 	}
 
-	total_eqs = dev->caps.num_comp_vectors + ibdev->eq_added;
-	memset(ibdev->eq_table, 0, total_eqs * sizeof(int));
 	kfree(ibdev->eq_table);
-
-	ibdev->eq_table = NULL;
-	ibdev->eq_added = 0;
 }
 
 static void *mlx4_ib_add(struct mlx4_dev *dev)