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=-3.8 required=3.0 tests=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 ADCC6C433FF for ; Tue, 6 Aug 2019 18:36:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8D2972086D for ; Tue, 6 Aug 2019 18:36:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1733069AbfHFSgl (ORCPT ); Tue, 6 Aug 2019 14:36:41 -0400 Received: from shards.monkeyblade.net ([23.128.96.9]:47820 "EHLO shards.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728558AbfHFSgl (ORCPT ); Tue, 6 Aug 2019 14:36:41 -0400 Received: from localhost (unknown [IPv6:2601:601:9f80:35cd::d71]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (Client did not present a certificate) (Authenticated sender: davem-davemloft) by shards.monkeyblade.net (Postfix) with ESMTPSA id E0BF0152488DC; Tue, 6 Aug 2019 11:36:40 -0700 (PDT) Date: Tue, 06 Aug 2019 11:36:40 -0700 (PDT) Message-Id: <20190806.113640.171591509807004446.davem@davemloft.net> To: firo.yang@suse.com Cc: netdev@vger.kernel.org, jeffrey.t.kirsher@intel.com, intel-wired-lan@lists.osuosl.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/1] ixgbe: sync the first fragment unconditionally From: David Miller In-Reply-To: <20190806092919.13211-1-firo.yang@suse.com> References: <20190806092919.13211-1-firo.yang@suse.com> X-Mailer: Mew version 6.8 on Emacs 26.1 Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Greylist: Sender succeeded SMTP AUTH, not delayed by milter-greylist-4.5.12 (shards.monkeyblade.net [149.20.54.216]); Tue, 06 Aug 2019 11:36:41 -0700 (PDT) Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org From: Firo Yang Date: Tue, 6 Aug 2019 09:29:51 +0000 > In Xen environment, if Xen-swiotlb is enabled, ixgbe driver > could possibly allocate a page, DMA memory buffer, for the first > fragment which is not suitable for Xen-swiotlb to do DMA operations. > Xen-swiotlb will internally allocate another page for doing DMA > operations. It requires syncing between those two pages. Otherwise, > we may get an incomplete skb. To fix this problem, sync the first > fragment no matter the first fargment is makred as "page_released" > or not. > > Signed-off-by: Firo Yang I don't understand, an unmap operation implies a sync operation.