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=-0.9 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, 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 029A7C43218 for ; Thu, 25 Apr 2019 20:04:59 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 0A61A206C0 for ; Thu, 25 Apr 2019 20:04:59 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="PgLuwWeU" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730897AbfDYUE5 (ORCPT ); Thu, 25 Apr 2019 16:04:57 -0400 Received: from mail-pg1-f170.google.com ([209.85.215.170]:37497 "EHLO mail-pg1-f170.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726490AbfDYUE4 (ORCPT ); Thu, 25 Apr 2019 16:04:56 -0400 Received: by mail-pg1-f170.google.com with SMTP id e6so386555pgc.4 for ; Thu, 25 Apr 2019 13:04:55 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=subject:to:cc:references:from:message-id:date:user-agent :mime-version:in-reply-to:content-language:content-transfer-encoding; bh=P8dVlAKIPiJzm0RxaP7Bl3BD8NcFCvaSYpsf8cTsWto=; b=PgLuwWeUfZiMpcowpn91zOYzfX/wI2Ik3PDuxic+FOou3vOfRc2gkLg2m/YHPe73Qj VWsuij2+o3cLRyUNWFqMwr3fcD1gitaryiLBZarcawMUPc/nsBCXcDldEeRN/u0wnJQU Q6YpdCwqAOYbW/dyUk1ViF7WJnBMj/ijfh2I8TGmE4o1CjzHuLcxuso76MncKAmdva4R wfU+FEtR/IzWbGa+NW3P6/GfPrRpHRX9K2CQXr9L+Hiw3SOBKUzPN0elEgx7fr0+sFL7 Ui81cBIanY0P/aFsU1Ow3dX9HqWdXlEOlNJSctSsNNFZl0/m9XWf33EzAM6d1vGUeYYB X7vw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=P8dVlAKIPiJzm0RxaP7Bl3BD8NcFCvaSYpsf8cTsWto=; b=Otxg11XhR81vcVlnilz0TwqbGCzM/cL25S/RDq0Ua4nrjpwXj3qTsNlzPzfL3/cYv1 nIw6MzBCseF0qQzo/qsjNBeYIeWXcjeXEAMqg/M/ylOs+1xTcFkSDAH6G8Xe6Yn4ktDO dqsSGSxwvoopkA85P8u0VLLeKfY+l+/5fBGd5yDLsYi5GwHhzkYqZmUIafZDYqS6cQ/Y QMVVvxlbBdrfl+lYDIl1T8XqzCBXSfmvRlZwFixeLLKnYL1teEkdicXiq2hJY/u3gb1t MbXmnDnUlZZ9RHl95ZW2abToHf6npDiaRBgrHTgGlrMRh7H9EOqlHDat71Cx3f/4yTVc iyJg== X-Gm-Message-State: APjAAAUgbyGUKnZnV4CDbkpCks0byn8zxPlvNC9JkIZYFL31+qX7UPcz CiHDYa4SsmxkN0Kk+3NWadw= X-Google-Smtp-Source: APXvYqypR+Oe6gNU8/TMYBKwfPpsf7evJ461BOwnWCqPpp7fPkLfr2rutLLbQE5TJ6JUMppU8TrKqA== X-Received: by 2002:a65:5046:: with SMTP id k6mr5391438pgo.325.1556222695390; Thu, 25 Apr 2019 13:04:55 -0700 (PDT) Received: from ?IPv6:2601:282:800:fd80:7cc1:255c:d029:91f7? ([2601:282:800:fd80:7cc1:255c:d029:91f7]) by smtp.googlemail.com with ESMTPSA id n3sm34437221pfa.99.2019.04.25.13.04.52 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 25 Apr 2019 13:04:53 -0700 (PDT) Subject: Re: virtio_net: suspicious RCU usage with xdp To: Maciej Fijalkowski Cc: Jesper Dangaard Brouer , "Michael S. Tsirkin" , Toshiaki Makita , =?UTF-8?Q?Toke_H=c3=b8iland-J=c3=b8rgensen?= , "netdev@vger.kernel.org" , Jason Wang References: <20190424132533-mutt-send-email-mst@kernel.org> <20190425130319-mutt-send-email-mst@kernel.org> <20190425194117.66093851@carbon> <8a0390d8-9d08-7ac9-6cc7-6d0612062226@gmail.com> <20190425205349.0000137c@gmail.com> From: David Ahern Message-ID: <4d6b3140-760e-1964-2bd7-fee94956e683@gmail.com> Date: Thu, 25 Apr 2019 14:04:52 -0600 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.14; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <20190425205349.0000137c@gmail.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On 4/25/19 12:54 PM, Maciej Fijalkowski wrote: >> >> virtio_net hits this because of: >> xdp_prog = rcu_dereference(rq->xdp_prog); >> >> in its ndo_xdp_xmit. Scanning ndo_xdp_xmit for other nics does not show >> this same check. Is it really required? If so, why don't other drivers >> do it? > > That was my initial thought as well. Can't we just check that > vi->xdp_queue_pairs was set in virtnet_xdp_xmit? It is being done just before > assigning the XDP prog pointers for rqs. Haven't looked at veth though. > or change the dereference to just rcu_access_pointer. The xdp_prog is not needed; it only checks if set.