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

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Date:	Wed, 14 Mar 2012 11:24:24 +0200
From:	Avi Kivity <avi@...hat.com>
To:	Wen Congyang <wency@...fujitsu.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>,
	Amit Shah <amit.shah@...hat.com>
Subject: Re: [PATCH 0/2 v3] kvm: notify host when guest panicked

On 03/14/2012 10:29 AM, Wen Congyang wrote:
> 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 don't either, copying Amit.

> 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?

Probably.

-- 
error compiling committee.c: too many arguments to function

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