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 <mtosatti@xxxxxxxxxx> writes: >> >>> On Tue, Aug 14, 2012 at 01:53:01PM -0500, Anthony Liguori wrote: >>>> Marcelo Tosatti <mtosatti@xxxxxxxxxx> 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@xxxxxxxxxxxxxxx >>>>>>> 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@xxxxxxxxxxxxxxx >> 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@xxxxxxxxxxxxxxx > 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 kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html