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=-11.8 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 C43DBC433E1 for ; Fri, 24 Jul 2020 07:16:57 +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 96B0B2073E for ; Fri, 24 Jul 2020 07:16:57 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 96B0B2073E 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]:47042 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1jyrwu-000731-PH for qemu-devel@archiver.kernel.org; Fri, 24 Jul 2020 03:16:56 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:46700) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1jyrwB-0006bj-Er for qemu-devel@nongnu.org; Fri, 24 Jul 2020 03:16:11 -0400 Received: from mga02.intel.com ([134.134.136.20]:37076) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1jyrw8-00057U-Na for qemu-devel@nongnu.org; Fri, 24 Jul 2020 03:16:11 -0400 IronPort-SDR: qc3qdtaKA+6R1KU4tGQooWtiGeTYoih1/NG6Dy/cca42kEZvo680GUrUsyYok1ZTTFwGIgsyhv Vqy6dGn9+pXA== X-IronPort-AV: E=McAfee;i="6000,8403,9691"; a="138734967" X-IronPort-AV: E=Sophos;i="5.75,389,1589266800"; d="scan'208";a="138734967" X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga003.fm.intel.com ([10.253.24.29]) by orsmga101.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 24 Jul 2020 00:16:00 -0700 IronPort-SDR: yTFHq0AP2LvEY0jZGzquJPvSzAwqNDiMNb3UgpHNiF3emY+orSi8FgfVxnZ832/j3b33zXudZe Jndwea6iMA5A== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.75,389,1589266800"; d="scan'208";a="327243559" Received: from jingqili-mobl.ccr.corp.intel.com (HELO [10.238.6.132]) ([10.238.6.132]) by FMSMGA003.fm.intel.com with ESMTP; 24 Jul 2020 00:15:59 -0700 Subject: Re: [PATCH] docs/nvdimm: add 'pmem=on' for the device dax backend file To: Paolo Bonzini , Xiao Guangrong , "Williams, Dan J" References: <20200715025429.28657-1-jingqi.liu@intel.com> From: "Liu, Jingqi" Message-ID: <7f5ec393-b145-b41b-ed91-259c916cb76f@intel.com> Date: Fri, 24 Jul 2020 15:15:59 +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=134.134.136.20; envelope-from=jingqi.liu@intel.com; helo=mga02.intel.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/07/24 03:16:01 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, RCVD_IN_MSPIKE_H3=-0.01, RCVD_IN_MSPIKE_WL=-0.01, 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" Ping for comments. 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 > ---------- >