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Date: Tue, 14 Aug 2012 13:53:01 -0500 From: Anthony Liguori <anthony@...emonkey.ws> To: Marcelo Tosatti <mtosatti@...hat.com>, Yan Vugenfirer <yvugenfi@...hat.com> Cc: kvm list <kvm@...r.kernel.org>, Jan Kiszka <jan.kiszka@...mens.com>, "linux-kernel\@vger.kernel.org" <linux-kernel@...r.kernel.org>, Gleb Natapov <gleb@...hat.com>, qemu-devel <qemu-devel@...gnu.org>, Avi Kivity <avi@...hat.com>, KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com> Subject: Re: [Qemu-devel] [PATCH v8] kvm: notify host when the guest is panicked Marcelo Tosatti <mtosatti@...hat.com> 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. 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. 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@...r.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@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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