netdev - RE: [PATCH v19 bpf-next 19/23] bpf: generalise tail call map compatibility check

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Date:   Mon, 06 Dec 2021 09:42:14 -0800
From:   John Fastabend <john.fastabend@...il.com>
To:     Lorenzo Bianconi <lorenzo@...nel.org>, bpf@...r.kernel.org,
        netdev@...r.kernel.org
Cc:     lorenzo.bianconi@...hat.com, davem@...emloft.net, kuba@...nel.org,
        ast@...nel.org, daniel@...earbox.net, shayagr@...zon.com,
        john.fastabend@...il.com, dsahern@...nel.org, brouer@...hat.com,
        echaudro@...hat.com, jasowang@...hat.com,
        alexander.duyck@...il.com, saeed@...nel.org,
        maciej.fijalkowski@...el.com, magnus.karlsson@...el.com,
        tirthendu.sarkar@...el.com, toke@...hat.com
Subject: RE: [PATCH v19 bpf-next 19/23] bpf: generalise tail call map
 compatibility check

Lorenzo Bianconi wrote:
> From: Toke Hoiland-Jorgensen <toke@...hat.com>
> 
> The check for tail call map compatibility ensures that tail calls only
> happen between maps of the same type. To ensure backwards compatibility for
> XDP multi-buffer we need a similar type of check for cpumap and devmap
> programs, so move the state from bpf_array_aux into bpf_map, add xdp_mb to
> the check, and apply the same check to cpumap and devmap.
> 
> Co-developed-by: Lorenzo Bianconi <lorenzo@...nel.org>
> Signed-off-by: Lorenzo Bianconi <lorenzo@...nel.org>
> Signed-off-by: Toke Hoiland-Jorgensen <toke@...hat.com>
> ---

...

> -bool bpf_prog_array_compatible(struct bpf_array *array, const struct bpf_prog *fp);
> +static inline bool map_type_contains_progs(struct bpf_map *map)

Maybe map_type_check_needed()? Just noticing that devmap doesn't contain
progs.

> +{
> +	return map->map_type == BPF_MAP_TYPE_PROG_ARRAY ||
> +	       map->map_type == BPF_MAP_TYPE_DEVMAP ||
> +	       map->map_type == BPF_MAP_TYPE_CPUMAP;
> +}
> +
> +bool bpf_prog_map_compatible(struct bpf_map *map, const struct bpf_prog *fp);
>  int bpf_prog_calc_tag(struct bpf_prog *fp);

Otherwise LGTM.