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

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Date:	Wed, 14 Mar 2012 15:16:05 +0200
From:	Avi Kivity <avi@...hat.com>
To:	Gleb Natapov <gleb@...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 03/14/2012 03:14 PM, Gleb Natapov wrote:
> On Wed, Mar 14, 2012 at 03:07:46PM +0200, Avi Kivity wrote:
> > On 03/14/2012 01:11 PM, Wen Congyang wrote:
> > > > 
> > > > I don't think we want to use the driver.  Instead, have a small piece of
> > > > code that resets the device and pushes out a string (the panic message?)
> > > > without any interrupts etc.
> > > > 
> > > > It's still going to be less reliable than a hypercall, I agree.
> > >
> > > Do you still want to use complicated and less reliable way?
> > 
> > Are you willing to try it out and see how complicated it really is?
> > 
> > While it's more complicated, it's also more flexible.  You can
> > communicate the panic message, whether the guest is attempting a kdump
> > and its own recovery or whether it wants the host to do it, etc., you
> > can communicate less severe failures like oopses.
> > 
> hypercall can take arguments to achieve the same.

It has to be designed in advance; and every time we notice something's
missing we have to update the host kernel.

> > > I think the other ones prefer to touch the hypervisor.
> > 
> > I understand the sentiment.  Your patches are simple and easy.  But my
> > feeling is that the kernel has become too complicated already and I'm
> > looking for ways to limit changes.
> > 
> Using virtio-serial will not reduce kernel complexity. Quite contrary
> since code that will use virtio-serial will be more complicated.

The host kernel is unmodified though.

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

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