linux-kernel - Re: linux next: Native Linux KVM tool inclusion request

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Date:	Wed, 24 Aug 2011 11:31:30 +0300
From:	Avi Kivity <avi@...hat.com>
To:	Pekka Enberg <penberg@...nel.org>
CC:	Christoph Hellwig <hch@...radead.org>,
	Sasha Levin <levinsasha928@...il.com>,
	Stephen Rothwell <sfr@...b.auug.org.au>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...e.hu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	linux-next@...r.kernel.org
Subject: Re: linux next: Native Linux KVM tool inclusion request

On 08/23/2011 08:08 AM, Pekka Enberg wrote:
> As for changes, we've implemented rootfs over 9p with "kvm run"
> booting to host filesystem "/bin/sh" by default.

Isn't this dangerous?  Users expect virtualization to land them in 
sandbox, but here an rm -rf / in the guest will happily junk the host 
filesystem.

> It still needs some
> work and we hope to enable networking too. We also have patches to use
> overlayfs so that the guest is able to use host filesystem in
> copy-on-write manner.
>

Still dangerous (but just to the guest), since it's not a true 
snapshot.  If the host filesystem changes underneath the guest, it will 
see partial and incoherent updates.  Copy-on-write only works if the 
host filesystem doesn't change.

-- 
I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.

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