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=-12.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=unavailable 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 D5634C433E1 for ; Tue, 28 Jul 2020 01:12:21 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id A732320714 for ; Tue, 28 Jul 2020 01:12:21 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org A732320714 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=intel.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:45696 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1k0EAH-0000WL-02 for qemu-devel@archiver.kernel.org; Mon, 27 Jul 2020 21:12:21 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:53442) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1k0E7k-0005eR-Ut for qemu-devel@nongnu.org; Mon, 27 Jul 2020 21:09:44 -0400 Received: from mga06.intel.com ([134.134.136.31]:61355) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1k0E7i-0001ph-AU for qemu-devel@nongnu.org; Mon, 27 Jul 2020 21:09:44 -0400 IronPort-SDR: +/4/sIRekadl6QuHEeutLBE211EJmWSFwurvufu8fo8+mSZZR/tM+F0EWRnb34EkR+ec54WXWv XwLonS2iyFDA== X-IronPort-AV: E=McAfee;i="6000,8403,9695"; a="212658095" X-IronPort-AV: E=Sophos;i="5.75,404,1589266800"; d="scan'208";a="212658095" X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga007.jf.intel.com ([10.7.209.58]) by orsmga104.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 27 Jul 2020 18:09:33 -0700 IronPort-SDR: 1Dazf2mhTEslFcuCB98A6IGK/VRIez9cT9+WHLdYFlww6E4QQW6zAhQzlS8nEnYP+W/uGGs2Ls r+MXWfAcVBBQ== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.75,404,1589266800"; d="scan'208";a="329874218" Received: from jingqili-mobl.ccr.corp.intel.com (HELO [10.238.6.132]) ([10.238.6.132]) by orsmga007.jf.intel.com with ESMTP; 27 Jul 2020 18:09:32 -0700 Subject: Re: [PATCH] docs/nvdimm: add 'pmem=on' for the device dax backend file To: Paolo Bonzini References: <20200715025429.28657-1-jingqi.liu@intel.com> From: "Liu, Jingqi" Message-ID: Date: Tue, 28 Jul 2020 09:09:31 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <20200715025429.28657-1-jingqi.liu@intel.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=134.134.136.31; envelope-from=jingqi.liu@intel.com; helo=mga06.intel.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/07/27 21:09:34 X-ACL-Warn: Detected OS = FreeBSD 9.x or newer [fuzzy] X-Spam_score_int: -41 X-Spam_score: -4.2 X-Spam_bar: ---- X-Spam_report: (-4.2 / 5.0 requ) BAYES_00=-1.9, RCVD_IN_DNSWL_MED=-2.3, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: "qemu-devel@nongnu.org" Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Hi Paolo, Any comments for this patch ? Thanks, Jingqi On 7/15/2020 10:54 AM, Liu, Jingqi wrote: > At the end of live migration, QEMU uses msync() to flush the data to > the backend storage. When the backend file is a character device dax, > the pages explicitly avoid the page cache. It will return failure from msync(). > The following warning is output. > > "warning: qemu_ram_msync: failed to sync memory range“ > > So we add 'pmem=on' to avoid calling msync(), use the QEMU command line: > > -object memory-backend-file,id=mem1,pmem=on,mem-path=/dev/dax0.0,size=4G > > Signed-off-by: Jingqi Liu > --- > docs/nvdimm.txt | 7 +++++++ > 1 file changed, 7 insertions(+) > > diff --git a/docs/nvdimm.txt b/docs/nvdimm.txt > index c2c6e441b3..31048aff5e 100644 > --- a/docs/nvdimm.txt > +++ b/docs/nvdimm.txt > @@ -243,6 +243,13 @@ use the QEMU command line: > > -object memory-backend-file,id=nv_mem,mem-path=/XXX/yyy,size=4G,pmem=on > > +At the end of live migration, QEMU uses msync() to flush the data to the > +backend storage. When the backend file is a character device dax, the pages > +explicitly avoid the page cache. It will return failure from msync(). > +So we add 'pmem=on' to avoid calling msync(), use the QEMU command line: > + > + -object memory-backend-file,id=mem1,pmem=on,mem-path=/dev/dax0.0,size=4G > + > References > ---------- >