linux-kernel - Re: [PATCH] kvm: notify host when guest paniced

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Message-ID: <20120229105235.GH24600@redhat.com>
Date:	Wed, 29 Feb 2012 12:52:35 +0200
From:	Gleb Natapov <gleb@...hat.com>
To:	Avi Kivity <avi@...hat.com>
Cc:	Wen Congyang <wency@...fujitsu.com>,
	kvm list <kvm@...r.kernel.org>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	"Daniel P. Berrange" <berrange@...hat.com>,
	linux-kernel@...r.kernel.org, qemu-devel <qemu-devel@...gnu.org>
Subject: Re: [PATCH] kvm: notify host when guest paniced

On Wed, Feb 29, 2012 at 12:48:57PM +0200, Avi Kivity wrote:
> On 02/29/2012 12:44 PM, Gleb Natapov wrote:
> > > > > 
> > > > Yes, crash can be so severe that it is not even detected by a kernel
> > > > itself, so not OOPS message even printed. But in most cases if kernel is
> > > > functional enough to print OOPS it is functional enough to call single
> > > > hypercall instruction.
> > > 
> > > Why not print the oops to virtio-serial?  Or even just a regular serial
> > > port?  That's what bare metal does.
> > > 
> > The more interface is complex the more chances it will fail during
> > panic. Regular serial is likely more reliable than virtio-serial.
> > Hypercall is likely more reliable than uart. On serial user can
> > fake panic notification. 
> 
> The serial device is under control of the kernel, so the user can only
> access it if the kernel so allows.
> 
Yes, but if we will hijack UART for panic notification VM user will not
be able to use it for anything else. virtio-serial have many channels,
but AFAIK it does not work at early stages of boot process.

--
			Gleb.
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