Re: [RFC PATCH] bpf: cpumap: report queue_index to xdp_rxq_info

[bot+bpf-ci]

> diff --git a/include/net/xdp.h b/include/net/xdp.h
> --- a/include/net/xdp.h
> +++ b/include/net/xdp.h
> @@ -297,10 +297,11 @@ struct xdp_frame {
>  	u32 headroom;
>  	u32 metasize; /* uses lower 8-bits */
>  	/* Lifetime of xdp_rxq_info is limited to NAPI/enqueue time,
> -	 * while mem_type is valid on remote CPU.
> +	 * while mem_type and queue_index are valid on remote CPU.
>  	 */
>  	enum xdp_mem_type mem_type:32;
>  	struct net_device *dev_rx; /* used by cpumap */
> +	u32 queue_index; /* used by cpumap */
>  	u32 frame_sz;
>  	u32 flags; /* supported values defined in xdp_buff_flags */
>  };

Is the updated comment accurate for all paths?

xdp_convert_buff_to_frame() has an early return for the zero-copy
path:

    if (xdp->rxq->mem.type == MEM_TYPE_XSK_BUFF_POOL)
        return xdp_convert_zc_to_xdp_frame(xdp);

xdp_convert_zc_to_xdp_frame() zeroes the frame with memset and
explicitly sets mem_type but never sets queue_index:

net/core/xdp.c:xdp_convert_zc_to_xdp_frame() {
    ...
    memset(xdpf, 0, sizeof(*xdpf));
    ...
    xdpf->mem_type = MEM_TYPE_PAGE_ORDER0;
    /* queue_index is not set -- remains 0 from memset */
    ...
}

The comment says queue_index is "valid on remote CPU" but for
zero-copy converted frames it will always be 0 regardless of which
hardware queue originated the packet.

> @@ -441,6 +442,7 @@ struct xdp_frame *xdp_convert_buff_to_frame(struct xdp_buff *xdp)
>
>  	/* rxq only valid until napi_schedule ends, convert to xdp_mem_type */
>  	xdp_frame->mem_type = xdp->rxq->mem.type;
> +	xdp_frame->queue_index = xdp->rxq->queue_index;
>
>  	return xdp_frame;

This assignment is only reached for the non-ZC path.  Should
xdp_convert_zc_to_xdp_frame() also set queue_index from
xdp->rxq->queue_index to match?


---
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