[net-next,v2,0/5] netdev_features: start cleaning netdev_features_t up

Message

Alexander Lobakin July 3, 2024, 3:03 p.m. UTC

NETDEV_FEATURE_COUNT is currently 64, which means we can't add any new
features as netdev_features_t is u64.
As per several discussions, instead of converting netdev_features_t to
a bitmap, which would mean A LOT of changes, we can try cleaning up
netdev feature bits.
There's a bunch of bits which don't really mean features, rather device
attributes/properties that can't be changed via Ethtool in any of the
drivers. Such attributes can be moved to netdev private flags without
losing any functionality.

Start converting some read-only netdev features to private flags from
the ones that are most obvious, like lockless Tx, inability to change
network namespace etc. I was able to reduce NETDEV_FEATURE_COUNT from
64 to 60, which mean 4 free slots for new features. There are obviously
more read-only features to convert, such as highDMA, "challenged VLAN",
HSR (4 bits) - this will be done in subsequent series.
Please note that netdev features are not uAPI/ABI by any means. Ethtool
passes their names and bits to the userspace separately and there are no
hardcoded names/bits in the userspace, so that new Ethtool could work
on older kernels and vice versa. Even shell scripts won't most likely
break since the removed bits were always read-only, meaning nobody would
try touching them from a script.

Alexander Lobakin (5):
  netdevice: convert private flags > BIT(31) to bitfields
  netdev_features: remove unused __UNUSED_NETIF_F_1
  netdev_features: convert NETIF_F_LLTX to dev->lltx
  netdev_features: convert NETIF_F_NETNS_LOCAL to dev->netns_local
  netdev_features: convert NETIF_F_FCOE_MTU to dev->fcoe_mtu

 .../networking/net_cachelines/net_device.rst  |  7 ++-
 Documentation/networking/netdev-features.rst  | 15 -------
 Documentation/networking/netdevices.rst       |  4 +-
 Documentation/networking/switchdev.rst        |  4 +-
 drivers/net/ethernet/tehuti/tehuti.h          |  2 +-
 include/linux/netdev_features.h               | 14 +-----
 include/linux/netdevice.h                     | 43 +++++++++++++------
 drivers/net/amt.c                             |  4 +-
 drivers/net/bareudp.c                         |  2 +-
 drivers/net/bonding/bond_main.c               |  8 ++--
 drivers/net/dummy.c                           |  3 +-
 drivers/net/ethernet/adi/adin1110.c           |  2 +-
 drivers/net/ethernet/chelsio/cxgb/cxgb2.c     |  3 +-
 .../net/ethernet/chelsio/cxgb4/cxgb4_fcoe.c   |  6 +--
 .../net/ethernet/freescale/dpaa/dpaa_eth.c    |  3 +-
 .../net/ethernet/freescale/dpaa2/dpaa2-eth.c  |  3 +-
 .../net/ethernet/intel/ixgbe/ixgbe_dcb_nl.c   |  2 +-
 drivers/net/ethernet/intel/ixgbe/ixgbe_fcoe.c |  4 +-
 drivers/net/ethernet/intel/ixgbe/ixgbe_lib.c  |  2 +-
 drivers/net/ethernet/intel/ixgbe/ixgbe_main.c | 11 ++---
 .../net/ethernet/intel/ixgbe/ixgbe_sriov.c    |  4 +-
 .../ethernet/marvell/prestera/prestera_main.c |  3 +-
 .../net/ethernet/mellanox/mlx5/core/en_main.c |  4 +-
 .../net/ethernet/mellanox/mlx5/core/en_rep.c  |  3 +-
 .../net/ethernet/mellanox/mlxsw/spectrum.c    |  6 ++-
 .../ethernet/microchip/lan966x/lan966x_main.c |  2 +-
 .../net/ethernet/netronome/nfp/nfp_net_repr.c |  3 +-
 drivers/net/ethernet/pasemi/pasemi_mac.c      |  5 ++-
 .../net/ethernet/qualcomm/rmnet/rmnet_vnd.c   |  2 +-
 drivers/net/ethernet/rocker/rocker_main.c     |  3 +-
 drivers/net/ethernet/sfc/ef100_rep.c          |  4 +-
 drivers/net/ethernet/tehuti/tehuti.c          |  4 +-
 drivers/net/ethernet/ti/cpsw_new.c            |  3 +-
 drivers/net/ethernet/toshiba/spider_net.c     |  3 +-
 drivers/net/geneve.c                          |  2 +-
 drivers/net/gtp.c                             |  2 +-
 drivers/net/hamradio/bpqether.c               |  2 +-
 drivers/net/ipvlan/ipvlan_main.c              |  3 +-
 drivers/net/loopback.c                        |  4 +-
 drivers/net/macsec.c                          |  4 +-
 drivers/net/macvlan.c                         |  6 ++-
 drivers/net/net_failover.c                    |  4 +-
 drivers/net/netkit.c                          |  3 +-
 drivers/net/nlmon.c                           |  4 +-
 drivers/net/ppp/ppp_generic.c                 |  2 +-
 drivers/net/rionet.c                          |  2 +-
 drivers/net/team/team_core.c                  |  8 ++--
 drivers/net/tun.c                             |  5 ++-
 drivers/net/veth.c                            |  2 +-
 drivers/net/vrf.c                             |  4 +-
 drivers/net/vsockmon.c                        |  4 +-
 drivers/net/vxlan/vxlan_core.c                |  5 ++-
 drivers/net/wireguard/device.c                |  2 +-
 drivers/scsi/fcoe/fcoe.c                      |  4 +-
 drivers/staging/octeon/ethernet.c             |  2 +-
 lib/test_bpf.c                                |  3 +-
 net/8021q/vlan_dev.c                          |  5 ++-
 net/8021q/vlanproc.c                          |  4 +-
 net/batman-adv/soft-interface.c               |  5 ++-
 net/bridge/br_device.c                        |  6 ++-
 net/core/dev.c                                |  8 ++--
 net/core/dev_ioctl.c                          |  9 ++--
 net/core/net-sysfs.c                          |  3 +-
 net/core/rtnetlink.c                          |  2 +-
 net/dsa/user.c                                |  3 +-
 net/ethtool/common.c                          |  3 --
 net/hsr/hsr_device.c                          | 12 +++---
 net/ieee802154/6lowpan/core.c                 |  2 +-
 net/ieee802154/core.c                         | 10 ++---
 net/ipv4/ip_gre.c                             |  4 +-
 net/ipv4/ip_tunnel.c                          |  2 +-
 net/ipv4/ip_vti.c                             |  2 +-
 net/ipv4/ipip.c                               |  2 +-
 net/ipv4/ipmr.c                               |  2 +-
 net/ipv6/ip6_gre.c                            |  7 +--
 net/ipv6/ip6_tunnel.c                         |  4 +-
 net/ipv6/ip6mr.c                              |  2 +-
 net/ipv6/sit.c                                |  4 +-
 net/l2tp/l2tp_eth.c                           |  2 +-
 net/openvswitch/vport-internal_dev.c          | 11 ++---
 net/wireless/core.c                           | 10 ++---
 net/xfrm/xfrm_interface_core.c                |  2 +-
 tools/testing/selftests/net/forwarding/README |  2 +-
 83 files changed, 204 insertions(+), 192 deletions(-)

---
From v1[0]:
* split bitfield priv flags into "hot" and "cold", leave the first
  placed where the old ::priv_flags is and move the rest down next
  to ::threaded (Jakub);
* document all the changes in Documentation/networking/net_cachelines/
  net_device.rst;
* #3: remove the "-1 cacheline on Tx" paragraph, not really true (Eric).

From RFC[1]:
* drop:
  * IFF_LOGICAL (as (LLTX | IFF_NO_QUEUE)) - will be discussed later;
  * NETIF_F_HIGHDMA conversion - requires priv flags inheriting etc.,
    maybe later;
  * NETIF_F_VLAN_CHALLENGED conversion - same as above;
* convert existing priv_flags > BIT(31) to bitfield booleans and define
  new flags the same way (Jakub);
* mention a couple times that netdev features are not uAPI/ABI by any
  means (Andrew).

[0] https://lore.kernel.org/netdev/[e-mail]
[1] https://lore.kernel.org/netdev/[e-mail]