net/mlx4_core: Turn off device-managed FS bit in dev-cap wrapper if DMFS is not enabled

Older kernels detect DMFS (device-managed flow steering) from the HCA
device capability directly, regardless of whether the capability was
enabled in INIT_HCA, this is fixed by commit 7b8157be "mlx4_core: Adjustments
to Flow Steering activation logic for SR-IOV"

To protect against guests running kernels without this fix, the host driver
should turn off the DMFS capability bit in mlx4_QUERY_DEV_CAP_wrapper.
Signed-off-by: Jack Morgenstein <jackm@dev.mellanox.co.il>
Signed-off-by: Or Gerlitz <ogerlitz@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

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

@@ -787,6 +787,14 @@ int mlx4_QUERY_DEV_CAP_wrapper(struct mlx4_dev *dev, int slave,
 	bmme_flags &= ~MLX4_BMME_FLAG_TYPE_2_WIN;
 	MLX4_PUT(outbox->buf, bmme_flags, QUERY_DEV_CAP_BMME_FLAGS_OFFSET);
 
+	/* turn off device-managed steering capability if not enabled */
+	if (dev->caps.steering_mode != MLX4_STEERING_MODE_DEVICE_MANAGED) {
+		MLX4_GET(field, outbox->buf,
+			 QUERY_DEV_CAP_FLOW_STEERING_RANGE_EN_OFFSET);
+		field &= 0x7f;
+		MLX4_PUT(outbox->buf, field,
+			 QUERY_DEV_CAP_FLOW_STEERING_RANGE_EN_OFFSET);
+	}
 	return 0;
 }