From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.8 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3B842ECE58E for ; Wed, 9 Oct 2019 07:31:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 155252133F for ; Wed, 9 Oct 2019 07:31:24 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="pnJLToe3" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728839AbfJIHbW (ORCPT ); Wed, 9 Oct 2019 03:31:22 -0400 Received: from mail-ot1-f65.google.com ([209.85.210.65]:32780 "EHLO mail-ot1-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725776AbfJIHbW (ORCPT ); Wed, 9 Oct 2019 03:31:22 -0400 Received: by mail-ot1-f65.google.com with SMTP id 60so888963otu.0; Wed, 09 Oct 2019 00:31:21 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=JPgub1MuIZH/1GWLVVbLyXVb5jS64cCM9E+ZqYGumsk=; b=pnJLToe3gYYe0/kNCVflu25Yx02qPhe36h8YMjVMiVP8o9umVeSha3sGUWYow1yGoI 6p1cPxZX5/ESpUK4aEDblN5obbLbBuz1zqAZlZkF56Bkq+9F4L0teKzdQ/fuNY1mtKrE +jtGtlG7uWEPdAtsYaQmqGEHpwzA63BDkGrfW7IAB9qvtUyBgfN3xaU30OVdeKruVzIq yUK8UurAMBfySG2jwlcMh40vwZgYFLXuAtAEnyMECaOO96VbjpmFk6BN6UF2XbGYb298 4ctgh3de230lnKmlc/Dk2FmVpRWBWO/b20XHELmitgQK3QDWG8YTFSQYHCGvIMpZm2mX uSpg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=JPgub1MuIZH/1GWLVVbLyXVb5jS64cCM9E+ZqYGumsk=; b=MCUKijVwoMl0HdMGugXcSloICw/sws4IaQhPSPJNeffdRRmmAzKYiIpwqj/cW7/KiU fRKOWZqXIEfQ8zI0box3bIslRxidoL2kR0HYOx1SfX7QX6C9DalmTeHhzNzb56oMLkjE tpf1a4X7bku6dIGQc6Y8WOtAixldFnhUf4aAlAB6m0OEHtVZiR4sjrP7pwg3xdmcYv47 gYtrpl1Io8/JKns+K9ejq1YP74m5XzrGE0FT47ru/n6nHExLqI5e2N0UIKoUCvOEoWvC /VHULt9G0FQiJGizbu9AmhsKloeKNg07rqhVmnt2/nqTQZ/kA16eraMdVFbQx89CjCTH Q/sg== X-Gm-Message-State: APjAAAVcU7aADw8IqX1/AAxJB9ezxgWu00eCMpSiT6HxJF1VLgZhzH9t 8rvFXzh/ERur5GA9tD2/snMa04VETu8/Z4BBRMM= X-Google-Smtp-Source: APXvYqwmIF7x7IYuQaNAEWMMUxk0A555Y6OeAN/AxF/6fNz5vD6G5GGXOzeidpKcF8jfcDSeN21jbhoahEVUK6nXWF8= X-Received: by 2002:a9d:7345:: with SMTP id l5mr1753864otk.39.1570606281434; Wed, 09 Oct 2019 00:31:21 -0700 (PDT) MIME-Version: 1.0 References: <1570530208-17720-1-git-send-email-magnus.karlsson@intel.com> <5d9ce369d6e5_17cc2aba94c845b415@john-XPS-13-9370.notmuch> In-Reply-To: <5d9ce369d6e5_17cc2aba94c845b415@john-XPS-13-9370.notmuch> From: Magnus Karlsson Date: Wed, 9 Oct 2019 09:31:10 +0200 Message-ID: Subject: Re: [PATCH bpf] libbpf: fix compatibility for kernels without need_wakeup To: John Fastabend Cc: Magnus Karlsson , =?UTF-8?B?QmrDtnJuIFTDtnBlbA==?= , Alexei Starovoitov , Daniel Borkmann , Network Development , Jonathan Lemon , bpf Content-Type: text/plain; charset="UTF-8" Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Tue, Oct 8, 2019 at 9:29 PM John Fastabend wrote: > > Magnus Karlsson wrote: > > When the need_wakeup flag was added to AF_XDP, the format of the > > XDP_MMAP_OFFSETS getsockopt was extended. Code was added to the kernel > > to take care of compatibility issues arrising from running > > applications using any of the two formats. However, libbpf was not > > extended to take care of the case when the application/libbpf uses the > > new format but the kernel only supports the old format. This patch > > adds support in libbpf for parsing the old format, before the > > need_wakeup flag was added, and emulating a set of static need_wakeup > > flags that will always work for the application. > > > > Fixes: a4500432c2587cb2a ("libbpf: add support for need_wakeup flag in AF_XDP part") > > Reported-by: Eloy Degen > > Signed-off-by: Magnus Karlsson > > --- > > tools/lib/bpf/xsk.c | 109 +++++++++++++++++++++++++++++++++++++--------------- > > 1 file changed, 78 insertions(+), 31 deletions(-) > > > > diff --git a/tools/lib/bpf/xsk.c b/tools/lib/bpf/xsk.c > > index a902838..46f9687 100644 > > --- a/tools/lib/bpf/xsk.c > > +++ b/tools/lib/bpf/xsk.c > > @@ -44,6 +44,25 @@ > > #define PF_XDP AF_XDP > > #endif > > > > +#define is_mmap_offsets_v1(optlen) \ > > + ((optlen) == sizeof(struct xdp_mmap_offsets_v1)) > > + > > +#define get_prod_off(ring) \ > > + (is_mmap_offsets_v1(optlen) ? \ > > + ((struct xdp_mmap_offsets_v1 *)&off)->ring.producer : \ > > + off.ring.producer) > > +#define get_cons_off(ring) \ > > + (is_mmap_offsets_v1(optlen) ? \ > > + ((struct xdp_mmap_offsets_v1 *)&off)->ring.consumer : \ > > + off.ring.consumer) > > +#define get_desc_off(ring) \ > > + (is_mmap_offsets_v1(optlen) ? \ > > + ((struct xdp_mmap_offsets_v1 *)&off)->ring.desc : off.ring.desc) > > +#define get_flags_off(ring) \ > > + (is_mmap_offsets_v1(optlen) ? \ > > + ((struct xdp_mmap_offsets_v1 *)&off)->ring.consumer + sizeof(u32) : \ > > + off.ring.flags) > > + > > It seems the only thing added was flags right? If so seems we > only need the last one there, get_flags_off(). I think it would > be a bit cleaner to just use the macros where its actually > needed IMO. The flag is indeed added to the end of struct xdp_ring_offsets, but this struct is replicated four times in the struct xdp_mmap_offsets, so the added flags are present four time there at different offsets. This means that 3 out of the 4 prod, cons and desc variables are located at different offsets from the original. Do not know how I can get rid of these macros in this case. But it might just be me not seeing it, of course :-). Thanks: Magnus > Thanks, > John