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=-0.8 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 CFE3BC433F5 for ; Fri, 7 Sep 2018 03:12:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 68AE820857 for ; Fri, 7 Sep 2018 03:12:35 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 68AE820857 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727518AbeIGHvM (ORCPT ); Fri, 7 Sep 2018 03:51:12 -0400 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:54604 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1725785AbeIGHvM (ORCPT ); Fri, 7 Sep 2018 03:51:12 -0400 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.rdu2.redhat.com [10.11.54.5]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 7E75F4023475; Fri, 7 Sep 2018 03:12:31 +0000 (UTC) Received: from [10.72.12.125] (ovpn-12-125.pek2.redhat.com [10.72.12.125]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 29D87A30DD; Fri, 7 Sep 2018 03:12:26 +0000 (UTC) Subject: Re: [PATCH net-next 02/11] tuntap: switch to use XDP_PACKET_HEADROOM To: "Michael S. Tsirkin" Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org, kvm@vger.kernel.org, virtualization@lists.linux-foundation.org References: <20180906040526.22518-1-jasowang@redhat.com> <20180906040526.22518-3-jasowang@redhat.com> <20180906125718-mutt-send-email-mst@kernel.org> From: Jason Wang Message-ID: <27def3eb-1b43-ec29-7380-c8078fe7ea8f@redhat.com> Date: Fri, 7 Sep 2018 11:12:24 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <20180906125718-mutt-send-email-mst@kernel.org> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.11.54.5 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.6]); Fri, 07 Sep 2018 03:12:31 +0000 (UTC) X-Greylist: inspected by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.6]); Fri, 07 Sep 2018 03:12:31 +0000 (UTC) for IP:'10.11.54.5' DOMAIN:'int-mx05.intmail.prod.int.rdu2.redhat.com' HELO:'smtp.corp.redhat.com' FROM:'jasowang@redhat.com' RCPT:'' Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2018年09月07日 00:57, Michael S. Tsirkin wrote: > On Thu, Sep 06, 2018 at 12:05:17PM +0800, Jason Wang wrote: >> Signed-off-by: Jason Wang > Acked-by: Michael S. Tsirkin > > any idea why didn't we do this straight away? Dunno, but git grep told me not all XDP capable driver use this (e.g virtio_net has its own value). Anyway, I think it's ok for driver to have their specific value if they can make sure the value is equal or greater than XDP_PACKET_HEADROOM. Thanks > >> --- >> drivers/net/tun.c | 3 +-- >> 1 file changed, 1 insertion(+), 2 deletions(-) >> >> diff --git a/drivers/net/tun.c b/drivers/net/tun.c >> index 2c548bd20393..d3677a544b56 100644 >> --- a/drivers/net/tun.c >> +++ b/drivers/net/tun.c >> @@ -113,7 +113,6 @@ do { \ >> } while (0) >> #endif >> >> -#define TUN_HEADROOM 256 >> #define TUN_RX_PAD (NET_IP_ALIGN + NET_SKB_PAD) >> >> /* TUN device flags */ >> @@ -1654,7 +1653,7 @@ static struct sk_buff *tun_build_skb(struct tun_struct *tun, >> rcu_read_lock(); >> xdp_prog = rcu_dereference(tun->xdp_prog); >> if (xdp_prog) >> - pad += TUN_HEADROOM; >> + pad += XDP_PACKET_HEADROOM; >> buflen += SKB_DATA_ALIGN(len + pad); >> rcu_read_unlock(); >> >> -- >> 2.17.1