linux-kernel - Re: [PATCH] staging: r8188eu: Add queue_index to xdp_rxq

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Date:   Thu, 2 Jun 2022 13:43:34 -0700
From:   Zvi Effron <zeffron@...tgames.com>
To:     Varshini Elangovan <varshini.elangovan@...il.com>
Cc:     ast@...nel.org, daniel@...earbox.net, davem@...emloft.net,
        kuba@...nel.org, hawk@...nel.org, john.fastabend@...il.com,
        andrii@...nel.org, kafai@...com, songliubraving@...com, yhs@...com,
        kpsingh@...nel.org, netdev@...r.kernel.org, bpf@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] staging: r8188eu: Add queue_index to xdp_rxq_info

On Thu, Jun 2, 2022 at 10:37 AM Varshini Elangovan
<varshini.elangovan@...il.com> wrote:
>
> Queue_index from the xdp_rxq_info is populated in cpumap file.
> Using the NR_CPUS, results in patch check warning, as recommended,
> using the num_possible_cpus() instead of NR_CPUS
>
> Signed-off-by: Varshini Elangovan <varshini.elangovan@...il.com>
> ---
> kernel/bpf/cpumap.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/kernel/bpf/cpumap.c b/kernel/bpf/cpumap.c
> index 650e5d21f90d..756fd81f474c 100644
> --- a/kernel/bpf/cpumap.c
> +++ b/kernel/bpf/cpumap.c
> @@ -102,8 +102,8 @@ static struct bpf_map *cpu_map_alloc(union bpf_attr *attr)
>
> bpf_map_init_from_attr(&cmap->map, attr);
>
> - /* Pre-limit array size based on NR_CPUS, not final CPU check */
> - if (cmap->map.max_entries > NR_CPUS) {
> + /* Pre-limit array size based on num_possible_cpus, not final CPU check */
> + if (cmap->map.max_entries > num_possible_cpus()) {
> err = -E2BIG;
> goto free_cmap;
> }
> @@ -227,7 +227,7 @@ static int cpu_map_bpf_prog_run_xdp(struct bpf_cpu_map_entry *rcpu,
>
> rxq.dev = xdpf->dev_rx;
> rxq.mem = xdpf->mem;
> - /* TODO: report queue_index to xdp_rxq_info */
> + rxq.queue_index = ++i;

I don't think this is correct. i is the frame index, not the queue index. There
is (as far as I can tell) no correlation between the two.

Additionally, i is the loop variable, and the ++ operator will change its
value, causing frames to be skipped.

>
> xdp_convert_frame_to_buff(xdpf, &xdp);

>
> --
> 2.25.1
>