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

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Date:	Wed, 29 Feb 2012 12:39:29 +0200
From:	Avi Kivity <avi@...hat.com>
To:	Wen Congyang <wency@...fujitsu.com>
CC:	Gleb Natapov <gleb@...hat.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 02/29/2012 12:17 PM, Wen Congyang 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.
>
> If virtio-serial's driver has bug or the guest doesn't have such device...

We have the same issue with the hypercall; and virtio-serial is
available on many deployed versions.

> > 
> >>>> Having special kdump
> >>>> kernel that transfers dump to a host via virtio-serial channel though
> >>>> sounds interesting. May be that's what you mean.
> >>>
> >>> Yes.  The "panic, starting dump" signal should be initiated by the
> >>> panicking kernel though, in case the dump fails.
> >>>
> >> Then panic hypercall sounds like a reasonable solution.
> > 
> > It is, but I'm trying to see if we can get away with doing nothing.
> > 
>
> If we have a reliable way with doing nothing, it is better. But I donot
> find such way.

We won't have a 100% reliable way.  But I think a variant of the driver
that doesn't use interrupts, or just using the ordinary serial driver,
should be reliable enough.

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

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