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

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Date:	Wed, 21 Mar 2012 11:18:16 -0500
From:	Corey Minyard <tcminyard@...il.com>
To:	Gleb Natapov <gleb@...hat.com>
CC:	Wen Congyang <wency@...fujitsu.com>,
	kvm list <kvm@...r.kernel.org>,
	qemu-devel <qemu-devel@...gnu.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Avi Kivity <avi@...hat.com>,
	"Daniel P. Berrange" <berrange@...hat.com>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Jan Kiszka <jan.kiszka@...mens.com>
Subject: Re: [PATCH 0/2 v3] kvm: notify host when guest panicked

> Look at drivers/char/ipmi/ipmi_msghandler.c. It has code to send panic
> event over IMPI. The code is pretty complex. Of course if we a going to
> implement something more complex than simple hypercall for panic
> notification we better do something more interesting with it than just
> saying "panic happened", like sending stack traces on all cpus for
> instance.

I doubt that's the best example, unfortunately.  The IPMI event log has 
limited space and it has to be send a little piece at a time since each 
log entry is 14 bytes.  It just prints the panic string, nothing else.  
Not that it isn't useful, it has saved my butt before.

You have lots of interesting options with paravirtualization.  You 
could, for instance, create a console driver that delivered all console 
output efficiently through a hypercall.  That would be really easy.  Or, 
as you mention, a custom way to deliver panic information.  Collecting 
information like stack traces would be harder to accomplish, as I don't 
think there is currently a way to get it except by sending it to printk.

-corey
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