netdev - Re: [PATCH bpf-next v6 07/17] bpf: XDP metadata RX kfuncs

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Message-ID: <bd002756-3295-b708-e304-976d42dbf121@linux.dev>
Date:   Thu, 5 Jan 2023 16:47:55 -0800
From:   Martin KaFai Lau <martin.lau@...ux.dev>
To:     Stanislav Fomichev <sdf@...gle.com>
Cc:     ast@...nel.org, daniel@...earbox.net, andrii@...nel.org,
        song@...nel.org, yhs@...com, john.fastabend@...il.com,
        kpsingh@...nel.org, haoluo@...gle.com, jolsa@...nel.org,
        David Ahern <dsahern@...il.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Willem de Bruijn <willemb@...gle.com>,
        Jesper Dangaard Brouer <brouer@...hat.com>,
        Anatoly Burakov <anatoly.burakov@...el.com>,
        Alexander Lobakin <alexandr.lobakin@...el.com>,
        Magnus Karlsson <magnus.karlsson@...il.com>,
        Maryam Tahhan <mtahhan@...hat.com>, xdp-hints@...-project.net,
        netdev@...r.kernel.org, bpf@...r.kernel.org
Subject: Re: [PATCH bpf-next v6 07/17] bpf: XDP metadata RX kfuncs

On 1/4/23 1:59 PM, Stanislav Fomichev wrote:
> +void *bpf_dev_bound_resolve_kfunc(struct bpf_prog *prog, u32 func_id)
> +{
> +	const struct xdp_metadata_ops *ops;
> +	void *p = NULL;
> +
> +	/* We don't hold bpf_devs_lock while resolving several
> +	 * kfuncs and can race with the unregister_netdevice().
> +	 * We rely on bpf_dev_bound_match() check at attach
> +	 * to render this program unusable.
> +	 */
> +	down_read(&bpf_devs_lock);
> +	if (!prog->aux->offload || !prog->aux->offload->netdev)

nit. !prog->aux->offload->netdev check is not needed. Testing 
!prog->aux->offload should be as good.