From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([140.186.70.92]:57239) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1RGUVt-00026S-7a for qemu-devel@nongnu.org; Wed, 19 Oct 2011 07:40:50 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1RGUVo-00069R-Eo for qemu-devel@nongnu.org; Wed, 19 Oct 2011 07:40:49 -0400 Received: from david.siemens.de ([192.35.17.14]:16093) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1RGUVo-000698-1L for qemu-devel@nongnu.org; Wed, 19 Oct 2011 07:40:44 -0400 Message-ID: <4E9EB72B.6010903@siemens.com> Date: Wed, 19 Oct 2011 13:40:27 +0200 From: Jan Kiszka MIME-Version: 1.0 References: <4E8ECA91.8040409@cn.fujitsu.com> <4E8ED167.1000705@siemens.com> <20111008151622.GA17181@amd.home.annexia.org> <4E916035.5050906@web.de> <20111009102338.GN16799@amd.home.annexia.org> <4E92568E.2010507@cn.fujitsu.com> <4E929618.4040403@web.de> <20111010090246.GF9408@redhat.com> <4E92BC11.3030508@siemens.com> <4E9D2791.5070207@cn.fujitsu.com> <4E9D3059.7050903@siemens.com> <4E9D31B4.1010000@cn.fujitsu.com> <4E9D3678.3010904@siemens.com> <4E9D3804.5040000@cn.fujitsu.com> <4E9D3847.8040202@siemens.com> <4E9D3965.4090003@cn.fujitsu.com> <4E9D394E.6050907@siemens.com> <20111019110401.b77f79fa.kamezawa.hiroyu@jp.fujitsu.com> In-Reply-To: <20111019110401.b77f79fa.kamezawa.hiroyu@jp.fujitsu.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [Question] dump memory when host pci device is used by guest List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: KAMEZAWA Hiroyuki Cc: Luiz Capitulino , qemu-devel , "Richard W.M. Jones" On 2011-10-19 04:04, KAMEZAWA Hiroyuki wrote: > On Tue, 18 Oct 2011 10:31:10 +0200 > Jan Kiszka wrote: > >> On 2011-10-18 10:31, Wen Congyang wrote: >>> At 10/18/2011 04:26 PM, Jan Kiszka Write: >>>> On 2011-10-18 10:25, Wen Congyang wrote: >>>>> At 10/18/2011 04:19 PM, Jan Kiszka Write: >>>>>> On 2011-10-18 09:58, Wen Congyang wrote: >>>>>>> At 10/18/2011 03:52 PM, Jan Kiszka Write: >>>>>>>> On 2011-10-18 09:15, Wen Congyang wrote: >>>>>>>>> Hi, Jan Kiszka >>>>>>>>> >>>>>>>>> At 10/10/2011 05:34 PM, Jan Kiszka Write: >>>>>>>>>> On 2011-10-10 11:02, Daniel P. Berrange wrote: >>>>>>>>>>> On Mon, Oct 10, 2011 at 08:52:08AM +0200, Jan Kiszka wrote: >>>>>>>>> >>>>>>>>>> >>>>>>>>>> Run gdb with "set debug remote 1" and watch the communication, it is not >>>>>>>>>> that complex. But a dump command is probably simpler for those >>>>>>>>>> scenarios, I agree. >>>>>>>>> >>>>>>>>> I have implemented the command dump and reuse migration's code. But I meet a problem >>>>>>>>> when I test it. >>>>>>>> >>>>>>>> Using migration code for dump is most probably the wrong approach as you >>>>>>>> saw through that conflict. All you need are the register states and the >>>>>>>> RAM. Reuse gdbstub services for this. >>>>>>> >>>>>>> Hmm, if the migration code can not be reused, I think we should define a new >>>>>>> qemu's vmcore format, and add some codes into crash to support such format. >>>>>> >>>>>> Please try to avoid defining something new. Unless there is a striking >>>>>> reason, standard gdb core files should be generated so that you can load >>>>>> the dump directly into gdb for analysis. >>>>> >>>>> I am not sure whehter the standard gdb core files can not be analyzed by crash. >>>>> If not, I think we should define something new because it's easier to use >>>>> crash than gdb to analyze the core files. >>>> >>>> gdb allows you to walk up the frame and print variables (globals & >>>> local) etc. >>> >>> Crash uses gdb to provide common function, and you can also use all the gdb commands >>> in crash. >> >> That what's the added value here when I can use gdb directly? >> > > I didn't read full story but 'crash' is used for investigating kernel core generated > by kdump for several years. Considering support service guys, virsh dump should support > a format for crash because they can't work well at investigating vmcore by gdb. > > crash has several functionality useful for them as 'show kerne log', 'focus on a cpu' > 'for-each-task', 'for-each-vma', 'extract ftrace log' etc. > > Anyway, if a man, who is not developper of qemu/kvm, should learn 2 tools for > investigating kernel dump, it sounds harmful. Right, that's why everything (live debugging & crash analysis) should be consolidated on the long run over gdb. crash is architecturally obsolete today - not saying it is useless! Jan -- Siemens AG, Corporate Technology, CT T DE IT 1 Corporate Competence Center Embedded Linux