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

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Message-ID: <4F4DF86C.5010407@redhat.com>
Date:	Wed, 29 Feb 2012 12:05:32 +0200
From:	Avi Kivity <avi@...hat.com>
To:	"Daniel P. Berrange" <berrange@...hat.com>
CC:	Wen Congyang <wency@...fujitsu.com>,
	kvm list <kvm@...r.kernel.org>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.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 11:58 AM, Daniel P. Berrange wrote:
> > 
> > How about using a virtio-serial channel for this?  You can transfer any
> > amount of information (including the dump itself).
>
> When the guest OS has crashed, any dumps will be done from the host
> OS using libvirt's core dump mechanism. The guest OS isn't involved
> and is likely too dead to be of any use anyway. Likewise it is
> quite probably too dead to work a virtio-serial channel or any
> similarly complex device. We're really just after the simplest
> possible notification that the guest kernel has paniced.

If it's alive enough to panic, it's alive enough to kexec its kdump
kernel.  After that it can do anything.

Guest-internal dumps are more useful IMO that host-initiated dumps.  In
a cloud, the host-initiated dump is left on the host, outside the reach
of the guest admin, outside the guest image where all the symbols are,
and sometimes not even on the same host if a live migration occurred. 
It's more useful in small setups, or if the problem is in the
hypervisor, not the guest.

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

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