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This is only needed > > when either these resources have to be configured or removed. It means > > that if one is switching XDP programs on-the-fly with running traffic, > > packets will be dropped. > > > > To avoid this, compare early on ice_xdp_setup_prog() state of incoming > > bpf_prog pointer vs the bpf_prog pointer that is already assigned to > > VSI. Do the swap in case VSI has bpf_prog and incoming one are non-NULL. > > > > Signed-off-by: Maciej Fijalkowski > > [0] :D > > But if be serious, are you sure you won't have any pointer tears / > partial reads/writes without such RCU protection as added in the > linked commit ? Since we removed rcu sections from driver sides and given an assumption that local_bh_{dis,en}able() pair serves this purpose now i believe this is safe. Are you aware of: https://lore.kernel.org/bpf/20210624160609.292325-1-toke@redhat.com/ ? > > > --- > > drivers/net/ethernet/intel/ice/ice_main.c | 12 +++++------- > > 1 file changed, 5 insertions(+), 7 deletions(-) > > > > diff --git a/drivers/net/ethernet/intel/ice/ice_main.c b/drivers/net/ethernet/intel/ice/ice_main.c > > index a1f7c8edc22f..8940ee505811 100644 > > --- a/drivers/net/ethernet/intel/ice/ice_main.c > > +++ b/drivers/net/ethernet/intel/ice/ice_main.c > > @@ -2922,6 +2922,11 @@ ice_xdp_setup_prog(struct ice_vsi *vsi, struct bpf_prog *prog, > > "MTU is too large for linear frames and XDP prog does not support frags"); > > return -EOPNOTSUPP; > > } > > + > > + /* hot swap progs and avoid toggling link */ > > + if (ice_is_xdp_ena_vsi(vsi) == !!prog) { > > + ice_vsi_assign_bpf_prog(vsi, prog); > > + return 0; > > } > > > > /* need to stop netdev while setting up the program for Rx rings */ > > @@ -2956,13 +2961,6 @@ ice_xdp_setup_prog(struct ice_vsi *vsi, struct bpf_prog *prog, > > xdp_ring_err = ice_realloc_zc_buf(vsi, false); > > if (xdp_ring_err) > > NL_SET_ERR_MSG_MOD(extack, "Freeing XDP Rx resources failed"); > > - } else { > > - /* safe to call even when prog == vsi->xdp_prog as > > - * dev_xdp_install in net/core/dev.c incremented prog's > > - * refcount so corresponding bpf_prog_put won't cause > > - * underflow > > - */ > > - ice_vsi_assign_bpf_prog(vsi, prog); > > } > > > > if (if_running) > > [0] > https://github.com/alobakin/linux/commit/5645adb0943dabeadfb9f6d00202c78fb9594fbe > > Thanks, > Olek