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

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Message-ID: <20120314104608.GU2304@redhat.com>
Date:	Wed, 14 Mar 2012 12:46:08 +0200
From:	Gleb Natapov <gleb@...hat.com>
To:	Avi Kivity <avi@...hat.com>
Cc:	Wen Congyang <wency@...fujitsu.com>,
	"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>,
	Amit Shah <amit.shah@...hat.com>
Subject: Re: [PATCH 0/2 v3] kvm: notify host when guest panicked

On Wed, Mar 14, 2012 at 12:29:57PM +0200, Avi Kivity wrote:
> On 03/14/2012 12:26 PM, Wen Congyang wrote:
> > >> If so, is this channel visible to guest userspace? If the channle is visible to guest
> > >> userspace, the program running in userspace may write the same message to the channel.
> > >>
> > > 
> > > Surely there's some kind of access control on channels.
> >
> > The virtio-serial depends on more things than touching the hypervisor. So I think touching
> > the hypervisor is more reliable than using virtio-serial device, and it is very simple and
> > easy to use.
> >
> > If we pass something from guest userspace to host, we can use virtio-serial. But If we pass
> > something from guest kernelspace to host, I still prefer to touch the hypervisor.
> 
> There's no argument that it's easier.  My concern is different, we're
> adding more and more stuff to the hypervisor because it's easier, which
> bloats it.  Every time we do it we add to compatibility and security
> problems.
> 
> The panic notification is *really* simple, so I don't expect it to cause
> a lot of problems.  But still, if it's possible not to change the
> hypervisor, we must make an effort in that direction.
> 
One more point against using virtio-serial is that it will be likely
compiled as a module which means panic during early boot will not be
reported.

--
			Gleb.
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