netdev - Re: [PATCH bpf-next 00/17] Clean up and document RCU-based object protection for XDP

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Date:   Wed, 9 Jun 2021 17:18:48 -0700
From:   Yonghong Song <yhs@...com>
To:     Toke Høiland-Jørgensen <toke@...hat.com>,
        <bpf@...r.kernel.org>, <netdev@...r.kernel.org>
CC:     Martin KaFai Lau <kafai@...com>,
        Hangbin Liu <liuhangbin@...il.com>,
        Jesper Dangaard Brouer <brouer@...hat.com>,
        Magnus Karlsson <magnus.karlsson@...il.com>,
        "Paul E . McKenney" <paulmck@...nel.org>
Subject: Re: [PATCH bpf-next 00/17] Clean up and document RCU-based object
 protection for XDP_REDIRECT



On 6/9/21 3:33 AM, Toke Høiland-Jørgensen wrote:
> During the discussion[0] of Hangbin's multicast patch series, Martin pointed out
> that the lifetime of the RCU-protected  map entries used by XDP_REDIRECT is by
> no means obvious. I promised to look into cleaning this up, and Paul helpfully
> provided some hints and a new unrcu_pointer() helper to aid in this.
> 
> This is mostly a documentation exercise, clearing up the description of the
> lifetime expectations and adding __rcu annotations so sparse and lockdep can
> help verify it.
> 
> Patches 1-2 are prepatory: Patch 1 adds Paul's unrcu_pointer() helper (which has
> already been added to his tree) and patch 2 is a small fix for
> dev_get_by_index_rcu() so lockdep understands _bh-disabled access to it. Patch 3
> is the main bit that adds the __rcu annotations and updates documentation
> comments, and the rest are patches updating the drivers, with one patch per
> distinct maintainer.
> 
> Unfortunately I don't have any hardware to test any of the driver patches;
> Jesper helpfully verified that it doesn't break anything on i40e, but the rest
> of the driver patches are only compile-tested.
> 
> [0] https://lore.kernel.org/bpf/20210415173551.7ma4slcbqeyiba2r@kafai-mbp.dhcp.thefacebook.com/
> 
> Paul E. McKenney (1):
>    rcu: Create an unrcu_pointer() to remove __rcu from a pointer
> 
> Toke Høiland-Jørgensen (16):
>    bpf: allow RCU-protected lookups to happen from bh context
>    dev: add rcu_read_lock_bh_held() as a valid check when getting a RCU
>      dev ref
>    xdp: add proper __rcu annotations to redirect map entries
>    ena: remove rcu_read_lock() around XDP program invocation
>    bnxt: remove rcu_read_lock() around XDP program invocation
>    thunderx: remove rcu_read_lock() around XDP program invocation
>    freescale: remove rcu_read_lock() around XDP program invocation
>    net: intel: remove rcu_read_lock() around XDP program invocation
>    marvell: remove rcu_read_lock() around XDP program invocation
>    mlx4: remove rcu_read_lock() around XDP program invocation
>    nfp: remove rcu_read_lock() around XDP program invocation
>    qede: remove rcu_read_lock() around XDP program invocation
>    sfc: remove rcu_read_lock() around XDP program invocation
>    netsec: remove rcu_read_lock() around XDP program invocation
>    stmmac: remove rcu_read_lock() around XDP program invocation
>    net: ti: remove rcu_read_lock() around XDP program invocation
> 
>   drivers/net/ethernet/amazon/ena/ena_netdev.c  |  3 --
>   drivers/net/ethernet/broadcom/bnxt/bnxt_xdp.c |  2 -
>   .../net/ethernet/cavium/thunder/nicvf_main.c  |  2 -
>   .../net/ethernet/freescale/dpaa/dpaa_eth.c    |  8 +--
>   .../net/ethernet/freescale/dpaa2/dpaa2-eth.c  |  3 --
>   drivers/net/ethernet/intel/i40e/i40e_txrx.c   |  2 -
>   drivers/net/ethernet/intel/i40e/i40e_xsk.c    |  6 +--
>   drivers/net/ethernet/intel/ice/ice_txrx.c     |  6 +--
>   drivers/net/ethernet/intel/ice/ice_xsk.c      |  6 +--
>   drivers/net/ethernet/intel/igb/igb_main.c     |  2 -
>   drivers/net/ethernet/intel/igc/igc_main.c     |  7 +--
>   drivers/net/ethernet/intel/ixgbe/ixgbe_main.c |  2 -
>   drivers/net/ethernet/intel/ixgbe/ixgbe_xsk.c  |  6 +--
>   .../net/ethernet/intel/ixgbevf/ixgbevf_main.c |  2 -
>   drivers/net/ethernet/marvell/mvneta.c         |  2 -
>   .../net/ethernet/marvell/mvpp2/mvpp2_main.c   |  4 --
>   drivers/net/ethernet/mellanox/mlx4/en_rx.c    |  8 +--
>   .../ethernet/netronome/nfp/nfp_net_common.c   |  2 -
>   drivers/net/ethernet/qlogic/qede/qede_fp.c    |  6 ---
>   drivers/net/ethernet/sfc/rx.c                 |  9 +---
>   drivers/net/ethernet/socionext/netsec.c       |  3 --
>   .../net/ethernet/stmicro/stmmac/stmmac_main.c | 10 +---
>   drivers/net/ethernet/ti/cpsw_priv.c           | 10 +---
>   include/linux/rcupdate.h                      | 14 +++++
>   include/net/xdp_sock.h                        |  2 +-
>   kernel/bpf/cpumap.c                           | 14 +++--
>   kernel/bpf/devmap.c                           | 52 ++++++++-----------
>   kernel/bpf/hashtab.c                          | 21 +++++---
>   kernel/bpf/helpers.c                          |  6 +--
>   kernel/bpf/lpm_trie.c                         |  6 ++-
>   net/core/dev.c                                |  2 +-
>   net/core/filter.c                             | 28 ++++++++++
>   net/xdp/xsk.c                                 |  4 +-
>   net/xdp/xsk.h                                 |  4 +-
>   net/xdp/xskmap.c                              | 29 ++++++-----
>   35 files changed, 134 insertions(+), 159 deletions(-)

Martin, could you help review this patch set? You had participated
in early discussions related to this patch. Thanks!