linux-kernel - Re: [RFC] Unify KVM kernel-space and user-space code into a single project

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Date:	Sun, 21 Mar 2010 23:03:19 +0200
From:	Avi Kivity <avi@...hat.com>
To:	Antoine Martin <antoine@...afix.co.uk>
CC:	Olivier Galibert <galibert@...ox.com>, Ingo Molnar <mingo@...e.hu>,
	Anthony Liguori <anthony@...emonkey.ws>,
	Pekka Enberg <penberg@...helsinki.fi>,
	"Zhang, Yanmin" <yanmin_zhang@...ux.intel.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Sheng Yang <sheng@...ux.intel.com>,
	linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
	Marcelo Tosatti <mtosatti@...hat.com>,
	oerg Roedel <joro@...tes.org>,
	Jes Sorensen <Jes.Sorensen@...hat.com>,
	Gleb Natapov <gleb@...hat.com>,
	Zachary Amsden <zamsden@...hat.com>, ziteng.huang@...el.com,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	Fr?d?ric Weisbecker <fweisbec@...il.com>
Subject: Re: [RFC] Unify KVM kernel-space and user-space code into a single
 project

On 03/21/2010 10:31 PM, Antoine Martin wrote:
> On 03/22/2010 03:24 AM, Avi Kivity wrote:
>> On 03/21/2010 10:18 PM, Antoine Martin wrote:
>>>> That includes the guest kernel.  If you can deploy a new kernel in 
>>>> the guest, presumably you can deploy a userspace package.
>>>
>>> That's not always true.
>>> The host admin can control the guest kernel via "kvm -kernel" easily 
>>> enough, but he may or may not have access to the disk that is used 
>>> in the guest. (think encrypted disks, service agreements, etc)
>>
>> There is a matching -initrd argument that you can use to launch a 
>> daemon.
> I thought this discussion was about making it easy to deploy... and 
> generating a custom initrd isn't easy by any means, and it requires 
> access to the guest filesystem (and its mkinitrd tools).

That's true.  You need to run mkinitrd anyway, though, unless your guest 
is non-modular and non-lvm.

>>   I believe that -kernel use will be rare, though.  It's a lot easier 
>> to keep everything in one filesystem.
> Well, for what it's worth, I rarely ever use anything else. My virtual 
> disks are raw so I can loop mount them easily, and I can also switch 
> my guest kernels from outside... without ever needing to mount those 
> disks.

Curious, what do you use them for?

btw, if you build your kernel outside the guest, then you already have 
access to all its symbols, without needing anything further.

-- 
Do not meddle in the internals of kernels, for they are subtle and quick to panic.

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