On Aug 14, 2012, at 10:35 PM, 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. > >> 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? > Actually there is a way (http://msdn.microsoft.com/en-us/library/windows/hardware/ff553105(v=vs.85).aspx). That's what I just mentioned already done in Windows virtio-net driver. Best regards, Yan. > 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 kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
