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

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Date:	Tue, 14 Aug 2012 17:01:50 +0200
From:	Jan Kiszka <jan.kiszka@...mens.com>
To:	Yan Vugenfirer <yvugenfi@...hat.com>
CC:	"Daniel P. Berrange" <berrange@...hat.com>,
	Marcelo Tosatti <mtosatti@...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 2012-08-14 16:55, 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.

What prevents writing the magic words to a second serial port in the
same way via that callback?

Jan

-- 
Siemens AG, Corporate Technology, CT RTC ITP SDP-DE
Corporate Competence Center Embedded Linux
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