linux-kernel - Re: [PATCH v8] kvm: notify host when the guest is panicked

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Message-ID: <20120814154237.GA21284@amt.cnet>
Date:	Tue, 14 Aug 2012 12:42:37 -0300
From:	Marcelo Tosatti <mtosatti@...hat.com>
To:	Yan Vugenfirer <yvugenfi@...hat.com>
Cc:	Jan Kiszka <jan.kiszka@...mens.com>,
	"Daniel P. Berrange" <berrange@...hat.com>,
	Wen Congyang <wency@...fujitsu.com>,
	kvm list <kvm@...r.kernel.org>,
	qemu-devel <qemu-devel@...gnu.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Avi Kivity <avi@...hat.com>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Gleb Natapov <gleb@...hat.com>
Subject: Re: [PATCH v8] kvm: notify host when the guest is panicked

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.

> 
> > 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
> > --
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