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? 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
