From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:60279) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1YbR5Q-0003Oi-Kx for qemu-devel@nongnu.org; Fri, 27 Mar 2015 06:01:57 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1YbR5M-0003co-2u for qemu-devel@nongnu.org; Fri, 27 Mar 2015 06:01:56 -0400 Received: from [59.151.112.132] (port=11231 helo=heian.cn.fujitsu.com) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1YbR5L-0003cM-NQ for qemu-devel@nongnu.org; Fri, 27 Mar 2015 06:01:51 -0400 Message-ID: <55152B4E.4050705@cn.fujitsu.com> Date: Fri, 27 Mar 2015 18:05:02 +0800 From: Wen Congyang MIME-Version: 1.0 References: <55128084.2040304@huawei.com> <87a8z12yot.fsf@neno.neno> <5513793B.6020909@cn.fujitsu.com> <874mp8xd9k.fsf@neno.neno> <20150327085634.GB3304@stefanha-thinkpad.redhat.com> <55151F59.8020000@cn.fujitsu.com> In-Reply-To: Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [Migration Bug? ] Occasionally, the content of VM's memory is inconsistent between Source and Destination of migration List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Stefan Hajnoczi Cc: Kevin Wolf , hangaohuai@huawei.com, zhanghailiang , Li Zhijian , Juan Quintela , Michael Tsirkin , qemu-devel , "Dr. David Alan Gilbert (git)" , "Gonglei (Arei)" , Stefan Hajnoczi , Amit Shah , "Huangpeng (Peter)" , David Gibson On 03/27/2015 05:57 PM, Stefan Hajnoczi wrote: > On Fri, Mar 27, 2015 at 9:14 AM, Wen Congyang wrote: >> On 03/27/2015 04:56 PM, Stefan Hajnoczi wrote: >>> On Thu, Mar 26, 2015 at 11:29:43AM +0100, Juan Quintela wrote: >>>> Wen Congyang wrote: >>>>> On 03/25/2015 05:50 PM, Juan Quintela wrote: >>>>>> zhanghailiang wrote: >>>>>>> Hi all, >>>>>>> >>>>>>> We found that, sometimes, the content of VM's memory is >>>>>>> inconsistent between Source side and Destination side >>>>>>> when we check it just after finishing migration but before VM continue to Run. >>>>>>> >>>>>>> We use a patch like bellow to find this issue, you can find it from affix, >>>>>>> and Steps to reprduce: >>>>>>> >>>>>>> (1) Compile QEMU: >>>>>>> ./configure --target-list=x86_64-softmmu --extra-ldflags="-lssl" && make >>>>>>> >>>>>>> (2) Command and output: >>>>>>> SRC: # x86_64-softmmu/qemu-system-x86_64 -enable-kvm -cpu >>>>>>> qemu64,-kvmclock -netdev tap,id=hn0-device >>>>>>> virtio-net-pci,id=net-pci0,netdev=hn0 -boot c -drive >>>>>>> file=/mnt/sdb/pure_IMG/sles/sles11_sp3.img,if=none,id=drive-virtio-disk0,cache=unsafe >>>>>>> -device >>>>>>> virtio-blk-pci,bus=pci.0,addr=0x4,drive=drive-virtio-disk0,id=virtio-disk0 >>>>>>> -vnc :7 -m 2048 -smp 2 -device piix3-usb-uhci -device usb-tablet >>>>>>> -monitor stdio >>>>>> >>>>>> Could you try to reproduce: >>>>>> - without vhost >>>>>> - without virtio-net >>>>>> - cache=unsafe is going to give you trouble, but trouble should only >>>>>> happen after migration of pages have finished. >>>>> >>>>> If I use ide disk, it doesn't happen. >>>>> Even if I use virtio-net with vhost=on, it still doesn't happen. I guess >>>>> it is because I migrate the guest when it is booting. The virtio net >>>>> device is not used in this case. >>>> >>>> Kevin, Stefan, Michael, any great idea? >>> >>> You must use -drive cache=none if you want to use live migration. It >>> should not directly affect memory during migration though. >> >> Otherwise, what will happen? If the user doesn't use cache=none, and >> tries to use live migration, qemu doesn't output any message or trigger >> an event to notify the user. > > There is a risk that the destination host sees an inconsistent view of > the image file because the source was still accessing it towards the > end of migration. Does the flag BDRV_O_NOFLUSH cause it? Thanks Wen Congyang > > Stefan > . >