[PATCH net-next] ethtool: tsconfig: always take rtnl_lock

[Jakub Kicinski <kuba@kernel.org>]

mlx5 throws ASSERT_RTNL() warnings on timestamp config, because
it tries to update features. mlx5e_hwtstamp_set() calls
netdev_update_features().

I missed this while grepping the drivers because tsconfig goes
through ndo_hwtstamp_set/get, not ethtool ops, even tho the new
uAPI is in ethtool Netlink. We could add a dedicated opt out bit
for mlx5, but NDOs were not supposed to be part of the ethtool locking
conversion in the first place.

The mlx5 features update is related to the "compressed CQE" format
which lacks timestamp, apparently. See commit c0194e2d0ef0 ("net/mlx5e:
Disable rxhash when CQE compress is enabled").

Fixes: 6e9e2eed4f39 ("net: ethtool: Add support for tsconfig command to get/set hwtstamp config")
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
---
CC: andrew@lunn.ch
CC: gal@nvidia.com
CC: jacob.e.keller@intel.com
CC: sdf@fomichev.me
CC: kory.maincent@bootlin.com
---
 net/ethtool/common.h | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/net/ethtool/common.h b/net/ethtool/common.h
index e3052972f953..2b3847f00801 100644
--- a/net/ethtool/common.h
+++ b/net/ethtool/common.h
@@ -113,6 +113,13 @@ ethtool_nl_msg_needs_rtnl(const struct net_device *dev, u8 cmd)
 		return ops->op_needs_rtnl & ETHTOOL_OP_NEEDS_RTNL_SPAUSEPARAM;
 	case ETHTOOL_MSG_RSS_SET:
 		return ops->op_needs_rtnl & ETHTOOL_OP_NEEDS_RTNL_RSS;
+	case ETHTOOL_MSG_TSCONFIG_GET:
+	case ETHTOOL_MSG_TSCONFIG_SET:
+		/* tsconfig calls ndos (ndo_hwtstamp_set/get), not ethtool ops.
+		 * Also, there is no corresponding ethtool ioctl, therefore
+		 * these cases are Netlink-only.
+		 */
+		return true;
 	}
 	return false;
 }
-- 
2.54.0