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=-3.9 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=no 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 6B245C2D0E8 for ; Fri, 3 Apr 2020 07:59:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 425F72073B for ; Fri, 3 Apr 2020 07:59:09 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="cOjU317M" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2390195AbgDCH7I (ORCPT ); Fri, 3 Apr 2020 03:59:08 -0400 Received: from us-smtp-1.mimecast.com ([205.139.110.61]:37903 "EHLO us-smtp-delivery-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S2389003AbgDCH7H (ORCPT ); Fri, 3 Apr 2020 03:59:07 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1585900745; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=mniN1sVbAvx++omfkPGQNGeast1vWCfMpGJZoMvG5sg=; b=cOjU317MV7u0YvNwWzGWs0WlENlf3gClsGJomRHx9i6UBGkm7y39mKSjzB6aicjrzgffPX SXMy0OowBaxA42ND5/KIP6xX00hCf6H542gNrpJA4+u2r6yeOl/8Dh4cU3yl+mUAAI5PUa iok5T83UDn08BOBmSsikF4HycnLFJ6Q= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-258-q4cbpdrYOIeVl-OSojS6fA-1; Fri, 03 Apr 2020 03:59:01 -0400 X-MC-Unique: q4cbpdrYOIeVl-OSojS6fA-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 2ED85800D5C; Fri, 3 Apr 2020 07:58:59 +0000 (UTC) Received: from carbon (unknown [10.40.208.16]) by smtp.corp.redhat.com (Postfix) with ESMTP id 6C5A85C1D6; Fri, 3 Apr 2020 07:58:49 +0000 (UTC) Date: Fri, 3 Apr 2020 09:58:47 +0200 From: Jesper Dangaard Brouer To: Alexei Starovoitov Cc: Toshiaki Makita , Mao Wenan , "David S. Miller" , Alexei Starovoitov , Daniel Borkmann , Jakub Kicinski , Jesper Dangaard Brouer , John Fastabend , Martin KaFai Lau , Song Liu , Yonghong Song , Andrii Nakryiko , jwi@linux.ibm.com, jianglidong3@jd.com, Eric Dumazet , Network Development , LKML , bpf , kernel-janitors@vger.kernel.org, brouer@redhat.com Subject: Re: [PATCH net v2] veth: xdp: use head instead of hard_start Message-ID: <20200403095847.21e1e5ea@carbon> In-Reply-To: References: <20200331060641.79999-1-maowenan@huawei.com> <7a1d55ad-1427-67fe-f204-4d4a0ab2c4b1@gmail.com> <20200401181419.7acd2aa6@carbon> <20200402110619.48f31a63@carbon> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 2 Apr 2020 08:40:23 -0700 Alexei Starovoitov wrote: > On Thu, Apr 2, 2020 at 2:06 AM Jesper Dangaard Brouer wrote: > > > > On Thu, 2 Apr 2020 09:47:03 +0900 > > Toshiaki Makita wrote: > > > > > On 2020/04/02 1:15, Jesper Dangaard Brouer wrote: > > > ... > > > > [PATCH RFC net-next] veth: adjust hard_start offset on redirect XDP frames > > > > > > > > When native XDP redirect into a veth device, the frame arrives in the > > > > xdp_frame structure. It is then processed in veth_xdp_rcv_one(), > > > > which can run a new XDP bpf_prog on the packet. Doing so requires > > > > converting xdp_frame to xdp_buff, but the tricky part is that > > > > xdp_frame memory area is located in the top (data_hard_start) memory > > > > area that xdp_buff will point into. > > > > > > > > The current code tried to protect the xdp_frame area, by assigning > > > > xdp_buff.data_hard_start past this memory. This results in 32 bytes > > > > less headroom to expand into via BPF-helper bpf_xdp_adjust_head(). > > > > > > > > This protect step is actually not needed, because BPF-helper > > > > bpf_xdp_adjust_head() already reserve this area, and don't allow > > > > BPF-prog to expand into it. Thus, it is safe to point data_hard_start > > > > directly at xdp_frame memory area. > > > > > > > > Cc: Toshiaki Makita > > > > > > FYI: This mail address is deprecated. > > > > > > > Fixes: 9fc8d518d9d5 ("veth: Handle xdp_frames in xdp napi ring") > > > > Reported-by: Mao Wenan > > > > Signed-off-by: Jesper Dangaard Brouer > > > > > > FWIW, > > > > > > Acked-by: Toshiaki Makita > > > > Thanks. > > > > I have updated your email and added your ack in my patchset. I will > > submit this officially once net-next opens up again[1], as part my > > larger patchset for introducing XDP frame_sz. > > It looks like bug fix to me. > The way I read it that behavior of bpf_xdp_adjust_head() is a bit > buggy with veth netdev, > so why wait ? I want to wait to ease your life as maintainer. This is part of a larger patchset (for XDP frame_sz) and the next patch touch same code path and thus depend on these code adjustments. If we apply them in bpf vs bpf-next then you/we will have to handle merge conflicts. The severity of the "fix" is really low, it only means 32 bytes less headroom (which I doubt anyone is using). -- Best regards, Jesper Dangaard Brouer MSc.CS, Principal Kernel Engineer at Red Hat LinkedIn: http://www.linkedin.com/in/brouer