Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752550Ab2HVG14 (ORCPT ); Wed, 22 Aug 2012 02:27:56 -0400 Received: from cn.fujitsu.com ([222.73.24.84]:54841 "EHLO song.cn.fujitsu.com" rhost-flags-OK-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1752041Ab2HVG1w (ORCPT ); Wed, 22 Aug 2012 02:27:52 -0400 X-IronPort-AV: E=Sophos;i="4.77,808,1336320000"; d="scan'208";a="5691496" Message-ID: <50347D24.6070808@cn.fujitsu.com> Date: Wed, 22 Aug 2012 14:33:08 +0800 From: Wen Congyang User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1.9) Gecko/20100413 Fedora/3.0.4-2.fc13 Thunderbird/3.0.4 MIME-Version: 1.0 To: Marcelo Tosatti CC: Anthony Liguori , Yan Vugenfirer , kvm list , Jan Kiszka , "linux-kernel@vger.kernel.org" , Gleb Natapov , qemu-devel , Avi Kivity , KAMEZAWA Hiroyuki Subject: Re: [Qemu-devel] [PATCH v8] kvm: notify host when the guest is panicked References: <5021D235.4050800@cn.fujitsu.com> <20120813182132.GB25268@amt.cnet> <20120814085619.GA32708@redhat.com> <502A2B7A.3070801@siemens.com> <86E2467F-0EA3-4A03-BD89-58E41F7DB808@redhat.com> <20120814154237.GA21284@amt.cnet> <87boidgvaq.fsf@codemonkey.ws> <20120814191927.GA6058@amt.cnet> <87txw5clmh.fsf@codemonkey.ws> <20120814205339.GA14172@amt.cnet> In-Reply-To: <20120814205339.GA14172@amt.cnet> X-MIMETrack: Itemize by SMTP Server on mailserver/fnst(Release 8.5.3|September 15, 2011) at 2012/08/22 14:27:49, Serialize by Router on mailserver/fnst(Release 8.5.3|September 15, 2011) at 2012/08/22 14:27:51, Serialize complete at 2012/08/22 14:27:51 Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 6298 Lines: 172 At 08/15/2012 04:53 AM, Marcelo Tosatti Wrote: > On Tue, Aug 14, 2012 at 02:35:34PM -0500, Anthony Liguori wrote: >> Marcelo Tosatti writes: >> >>> On Tue, Aug 14, 2012 at 01:53:01PM -0500, Anthony Liguori wrote: >>>> Marcelo Tosatti writes: >>>> >>>>> On Tue, Aug 14, 2012 at 05:55:54PM +0300, Yan Vugenfirer wrote: >>>>>> >>>>>> On Aug 14, 2012, at 1:42 PM, Jan Kiszka wrote: >>>>>> >>>>>>> On 2012-08-14 10:56, Daniel P. Berrange wrote: >>>>>>>> On Mon, Aug 13, 2012 at 03:21:32PM -0300, Marcelo Tosatti wrote: >>>>>>>>> On Wed, Aug 08, 2012 at 10:43:01AM +0800, Wen Congyang wrote: >>>>>>>>>> We can know the guest is panicked when the guest runs on xen. >>>>>>>>>> But we do not have such feature on kvm. >>>>>>>>>> >>>>>>>>>> Another purpose of this feature is: management app(for example: >>>>>>>>>> libvirt) can do auto dump when the guest is panicked. If management >>>>>>>>>> app does not do auto dump, the guest's user can do dump by hand if >>>>>>>>>> he sees the guest is panicked. >>>>>>>>>> >>>>>>>>>> We have three solutions to implement this feature: >>>>>>>>>> 1. use vmcall >>>>>>>>>> 2. use I/O port >>>>>>>>>> 3. use virtio-serial. >>>>>>>>>> >>>>>>>>>> We have decided to avoid touching hypervisor. The reason why I choose >>>>>>>>>> choose the I/O port is: >>>>>>>>>> 1. it is easier to implememt >>>>>>>>>> 2. it does not depend any virtual device >>>>>>>>>> 3. it can work when starting the kernel >>>>>>>>> >>>>>>>>> How about searching for the "Kernel panic - not syncing" string >>>>>>>>> in the guests serial output? Say libvirtd could take an action upon >>>>>>>>> that? >>>>>>>> >>>>>>>> No, this is not satisfactory. It depends on the guest OS being >>>>>>>> configured to use the serial port for console output which we >>>>>>>> cannot mandate, since it may well be required for other purposes. >>>>>>> >>>>>> Please don't forget Windows guests, there is no console and no "Kernel Panic" string ;) >>>>>> >>>>>> What I used for debugging purposes on Windows guest is to register a bugcheck callback in virtio-net driver and write 1 to VIRTIO_PCI_ISR register. >>>>>> >>>>>> Yan. >>>>> >>>>> Considering whether a "panic-device" should cover other OSes is also \ >>> >>>>> something to consider. Even for Linux, is "panic" the only case which >>>>> should be reported via the mechanism? What about oopses without panic? >>>>> >>>>> Is the mechanism general enough for supporting new events, etc. >>>> >>>> Hi, >>>> >>>> I think this discussion is gone of the deep end. >>>> >>>> Forget about !x86 platforms. They have their own way to do this sort of >>>> thing. >>> >>> The panic function in kernel/panic.c has the following options, which >>> appear to be arch independent, on panic: >>> >>> - reboot >>> - blink >> >> Not sure the semantics of blink but that might be a good place for a >> pvops hook. >> >>> >>> None are paravirtual interfaces however. >>> >>>> Think of this feature like a status LED on a motherboard. These >>>> are very common and usually controlled by IO ports. >>>> >>>> We're simply reserving a "status LED" for the guest to indicate that it >>>> has paniced. Let's not over engineer this. >>> >>> My concern is that you end up with state that is dependant on x86. >>> >>> Subject: [PATCH v8 3/6] add a new runstate: RUN_STATE_GUEST_PANICKED >>> >>> Having the ability to stop/restart the guest (and even introducing a >>> new VM runstate) is more than a status LED analogy. >> >> I must admit, I don't know why a new runstate is necessary/useful. The >> kernel shouldn't have to care about the difference between a halted guest >> and a panicked guest. That level of information belongs in userspace IMHO. >> >>> Can this new infrastructure be used by other architectures? >> >> I guess I don't understand why the kernel side of this isn't anything >> more than a paravirt op hook that does a single outb() with the >> remaining logic handled 100% in QEMU. > >>From the patch description: > > "Another purpose of this feature is: management app(for example: > libvirt) can do auto dump when the guest is panicked. If management > app does not do auto dump, the guest's user can do dump by hand if > he sees the guest is panicked." > > Wen, auto dump means dump of guest memory? Yes. > > In that case, the notification should obviously stop the guest > otherwise the guest might be reset by the time memdump from QEMU > monitor runs. Yes, the guest is stopped while auto dumping. > > But kexec supports dumping of memory already (i suppose it can > do automatic dump+{reboot,shutdown}). It can be easily done in management app. Thanks Wen Congyang > >>> Do you consider allowing support for Windows as overengineering? >> >> I don't think there is a way to hook BSOD on Windows so attempting to >> engineer something that works with Windows seems odd, no? > > Unsure about hooking at BSOD time. But Windows has configurable > memory dump/reset/reboot, so yes it should not necessary. > >> >> Regards, >> >> Anthony Liguori >> >>> >>>> Regards, >>>> >>>> Anthony Liguori >>>> >>>>> >>>>>> >>>>>>> Well, we have more than a single serial port, even when leaving >>>>>>> virtio-serial aside... >>>>>>> >>>>>>> Jan >>>>>>> >>>>>>> -- >>>>>>> Siemens AG, Corporate Technology, CT RTC ITP SDP-DE >>>>>>> Corporate Competence Center Embedded Linux >>>>>>> -- >>>>>>> To unsubscribe from this list: send the line "unsubscribe kvm" in >>>>>>> the body of a message to majordomo@vger.kernel.org >>>>>>> More majordomo info at http://vger.kernel.org/majordomo-info.html >> -- >> To unsubscribe from this list: send the line "unsubscribe kvm" in >> the body of a message to majordomo@vger.kernel.org >> More majordomo info at http://vger.kernel.org/majordomo-info.html > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/