From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <SRS0=wgvw=S4=vger.kernel.org=netdev-owner@kernel.org>
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=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS,
	MAILING_LIST_MULTI,SPF_PASS autolearn=ham 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 0E4AEC43218
	for <netdev@archiver.kernel.org>; Fri, 26 Apr 2019 08:00:39 +0000 (UTC)
Received: from vger.kernel.org (vger.kernel.org [209.132.180.67])
	by mail.kernel.org (Postfix) with ESMTP id D98E2206BA
	for <netdev@archiver.kernel.org>; Fri, 26 Apr 2019 08:00:38 +0000 (UTC)
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
        id S1725985AbfDZIAh (ORCPT <rfc822;netdev@archiver.kernel.org>);
        Fri, 26 Apr 2019 04:00:37 -0400
Received: from mx1.redhat.com ([209.132.183.28]:53725 "EHLO mx1.redhat.com"
        rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP
        id S1725854AbfDZIAh (ORCPT <rfc822;netdev@vger.kernel.org>);
        Fri, 26 Apr 2019 04:00:37 -0400
Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22])
        (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits))
        (No client certificate requested)
        by mx1.redhat.com (Postfix) with ESMTPS id 661073086272;
        Fri, 26 Apr 2019 08:00:37 +0000 (UTC)
Received: from [10.72.12.130] (ovpn-12-130.pek2.redhat.com [10.72.12.130])
        by smtp.corp.redhat.com (Postfix) with ESMTP id 8A0951001E7C;
        Fri, 26 Apr 2019 08:00:30 +0000 (UTC)
Subject: Re: virtio_net: suspicious RCU usage with xdp
To:     Jesper Dangaard Brouer <brouer@redhat.com>,
        "Michael S. Tsirkin" <mst@redhat.com>
Cc:     Toshiaki Makita <makita.toshiaki@lab.ntt.co.jp>,
        David Ahern <dsahern@gmail.com>,
        =?UTF-8?Q?Toke_H=c3=b8iland-J=c3=b8rgensen?= <toke@toke.dk>,
        "netdev@vger.kernel.org" <netdev@vger.kernel.org>
References: <a03cb5b3-5aa5-7d8f-10db-65d54846807a@gmail.com>
 <20190424132533-mutt-send-email-mst@kernel.org>
 <e018f919-a99b-e1bb-9ef1-fb36e252377e@lab.ntt.co.jp>
 <20190425130319-mutt-send-email-mst@kernel.org>
 <20190425194117.66093851@carbon>
From:   Jason Wang <jasowang@redhat.com>
Message-ID: <8bcd6aba-ea18-7e20-b883-3b926b9a2c07@redhat.com>
Date:   Fri, 26 Apr 2019 16:00:28 +0800
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101
 Thunderbird/60.6.1
MIME-Version: 1.0
In-Reply-To: <20190425194117.66093851@carbon>
Content-Type: text/plain; charset=utf-8; format=flowed
Content-Transfer-Encoding: 8bit
Content-Language: en-US
X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22
X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.49]); Fri, 26 Apr 2019 08:00:37 +0000 (UTC)
Sender: netdev-owner@vger.kernel.org
Precedence: bulk
List-ID: <netdev.vger.kernel.org>
X-Mailing-List: netdev@vger.kernel.org


On 2019/4/26 上午1:41, Jesper Dangaard Brouer wrote:
> It does sound like my commit 5d053f9da431 ("bpf: devmap prepare xdp
> frames for bulking") introduced this issue.  I guess we can add the RCU
> section to xdp_do_flush_map(), and then also verify that the devmap
> (and cpumap) take-down code also have appropriate RCU sections (which
> they should have).
>
> Another requirement for calling .ndo_xdp_xmit is running under NAPI
> protection,


May I know the reason for this? I'm asking since if the packet was 
redirected from tuntap, ndo_xdp_xmit()  won't be called under the 
protection of NAPI (but bh is disabled).

Thanks


> is that still satisifed for veth?
> (even when invoked via xdp_do_flush_map()).