Re: [PATCH] [RFC PATCH] bpf/xdp: propagate queue_index via xdp_frame for cpumap

[Alexei Starovoitov]

On Mon, Apr 6, 2026 at 10:12 AM Adith-Joshua <adithalex29@xxxxxxxxx> wrote:
>
> cpu_map_bpf_prog_run_xdp() currently lacks queue_index information in
> xdp_rxq_info, as struct xdp_frame does not preserve it across the
> xdp_buff -> xdp_frame conversion.
>
> This results in loss of rx queue metadata when frames are redirected
> via cpumap and later processed by XDP programs.
>
> Propagate queue_index by storing it in struct xdp_frame during
> conversion and restoring it when reconstructing xdp_buff. All
> relevant xdp_frame constructors have been updated to ensure the field is consistently
> initialized.
>
> This introduces a new field in struct xdp_frame, which may have
> implications for structure size and layout. Field reordering was
> considered to minimize padding, but is not included here to keep the
> change focused and avoid unrelated modifications.
>
> Feedback is appreciated on whether this approach is acceptable or if a
> different mechanism or struct layout would be preferred.
>
> Signed-off-by: Adith-Joshua <adithalex29@xxxxxxxxx>
> ---
>  include/net/xdp.h     |  4 ++++
>  kernel/bpf/cpumap.c   |  2 +-
>  kernel/bpf/verifier.c | 12 ++++++++----
>  net/core/xdp.c        |  1 +
>  4 files changed, 14 insertions(+), 5 deletions(-)
>
> diff --git a/include/net/xdp.h b/include/net/xdp.h
> index aa742f413c35..11aecf84a896 100644
> --- a/include/net/xdp.h
> +++ b/include/net/xdp.h
> @@ -301,6 +301,7 @@ struct xdp_frame {
>          */
>         enum xdp_mem_type mem_type:32;
>         struct net_device *dev_rx; /* used by cpumap */
> +       u32 queue_index;
>         u32 frame_sz;
>         u32 flags; /* supported values defined in xdp_buff_flags */
>  };
> @@ -347,6 +348,7 @@ static inline void xdp_scrub_frame(struct xdp_frame *frame)
>  {
>         frame->data = NULL;
>         frame->dev_rx = NULL;
> +       frame->queue_index = 0;
>  }
>
>  static inline void
> @@ -392,6 +394,7 @@ void xdp_convert_frame_to_buff(const struct xdp_frame *frame,
>         xdp->data = frame->data;
>         xdp->data_end = frame->data + frame->len;
>         xdp->data_meta = frame->data - frame->metasize;
> +       xdp->rxq->queue_index = frame->queue_index;
>         xdp->frame_sz = frame->frame_sz;
>         xdp->flags = frame->flags;
>  }
> @@ -419,6 +422,7 @@ int xdp_update_frame_from_buff(const struct xdp_buff *xdp,
>         xdp_frame->len  = xdp->data_end - xdp->data;
>         xdp_frame->headroom = headroom - sizeof(*xdp_frame);
>         xdp_frame->metasize = metasize;
> +       xdp_frame->queue_index = xdp->rxq->queue_index;
>         xdp_frame->frame_sz = xdp->frame_sz;
>         xdp_frame->flags = xdp->flags;
>
> diff --git a/kernel/bpf/cpumap.c b/kernel/bpf/cpumap.c
> index 32b43cb9061b..e475a732ceca 100644
> --- a/kernel/bpf/cpumap.c
> +++ b/kernel/bpf/cpumap.c
> @@ -197,7 +197,7 @@ static int cpu_map_bpf_prog_run_xdp(struct bpf_cpu_map_entry *rcpu,
>
>                 rxq.dev = xdpf->dev_rx;
>                 rxq.mem.type = xdpf->mem_type;
> -               /* TODO: report queue_index to xdp_rxq_info */
> +               rxq.queue_index = xdpf->queue_index;
>

nack. please do your homework and research the mailing list first.
Other people already attempted removing this.

pw-bot: cr