linux-kernel - Re: [PATCH 0/2 v3] kvm: notify host when guest panicked

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Date:	Wed, 14 Mar 2012 16:29:50 +0800
From:	Wen Congyang <wency@...fujitsu.com>
To:	Avi Kivity <avi@...hat.com>
CC:	"Daniel P. Berrange" <berrange@...hat.com>,
	kvm list <kvm@...r.kernel.org>,
	qemu-devel <qemu-devel@...gnu.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Jan Kiszka <jan.kiszka@...mens.com>,
	Gleb Natapov <gleb@...hat.com>
Subject: Re: [PATCH 0/2 v3] kvm: notify host when guest panicked

At 03/13/2012 06:47 PM, Avi Kivity Wrote:
> On 03/13/2012 11:18 AM, Daniel P. Berrange wrote:
>> On Mon, Mar 12, 2012 at 12:33:33PM +0200, Avi Kivity wrote:
>>> On 03/12/2012 11:04 AM, Wen Congyang wrote:
>>>> Do you have any other comments about this patch?
>>>>
>>>
>>> Not really, but I'm not 100% convinced the patch is worthwhile.  It's
>>> likely to only be used by Linux, which has kexec facilities, and you can
>>> put talk to management via virtio-serial and describe the crash in more
>>> details than a simple hypercall.
>>
>> As mentioned before, I don't think virtio-serial is a good fit for this.
>> We want something that is simple & guaranteed always available. Using
>> virtio-serial requires significant setup work on both the host and guest.
> 
> So what?  It needs to be done anyway for the guest agent.
> 
>> Many management application won't know to make a vioserial device available
>> to all guests they create. 
> 
> Then they won't know to deal with the panic event either.
> 
>> Most administrators won't even configure kexec,
>> let alone virtio serial on top of it. 
> 
> It should be done by the OS vendor, not the individual admin.
> 
>> The hypercall requires zero host
>> side config, and zero guest side config, which IMHO is what we need for
>> this feature.
> 
> If it was this one feature, yes.  But we keep getting more and more
> features like that and we bloat the hypervisor.  There's a reason we
> have a host-to-guest channel, we should use it.
> 

I donot know how to use virtio-serial.

I start vm like this:
qemu ...\
   -device virtio-serial \
  -chardev socket,path=/tmp/foo,server,nowait,id=foo \
  -device virtserialport,chardev=foo,name=port1 ...

You said that there are too many channels. Does it mean /tmp/foo is a channel?

Thanks
Wen Congyang
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