From mboxrd@z Thu Jan  1 00:00:00 1970
Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43)
	id 1O4e4M-0003Es-DH
	for qemu-devel@nongnu.org; Wed, 21 Apr 2010 13:50:38 -0400
Received: from [140.186.70.92] (port=33825 helo=eggs.gnu.org)
	by lists.gnu.org with esmtp (Exim 4.43) id 1O4e4K-0003DR-Vj
	for qemu-devel@nongnu.org; Wed, 21 Apr 2010 13:50:38 -0400
Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.69)
	(envelope-from <jamie@shareable.org>) id 1O4e4F-0001Ud-Tq
	for qemu-devel@nongnu.org; Wed, 21 Apr 2010 13:50:36 -0400
Received: from mail2.shareable.org ([80.68.89.115]:49701)
	by eggs.gnu.org with esmtp (Exim 4.69)
	(envelope-from <jamie@shareable.org>) id 1O4e4F-0001UU-Jq
	for qemu-devel@nongnu.org; Wed, 21 Apr 2010 13:50:31 -0400
Date: Wed, 21 Apr 2010 18:50:30 +0100
From: Jamie Lokier <jamie@shareable.org>
Subject: Re: [Qemu-devel] Re: [PATCH 04/22] savevm: do_loadvm(): Always resume
	the VM
Message-ID: <20100421175030.GE27575@shareable.org>
References: <1271797792-24571-1-git-send-email-lcapitulino@redhat.com>
	<1271797792-24571-5-git-send-email-lcapitulino@redhat.com>
	<4BCEFD70.70100@redhat.com> <20100421120838.4aa8428c@redhat.com>
	<m3iq7kolm4.fsf@trasno.mitica>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <m3iq7kolm4.fsf@trasno.mitica>
List-Id: qemu-devel.nongnu.org
List-Unsubscribe: <http://lists.nongnu.org/mailman/listinfo/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=unsubscribe>
List-Archive: <http://lists.gnu.org/pipermail/qemu-devel>
List-Post: <mailto:qemu-devel@nongnu.org>
List-Help: <mailto:qemu-devel-request@nongnu.org?subject=help>
List-Subscribe: <http://lists.nongnu.org/mailman/listinfo/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=subscribe>
To: Juan Quintela <quintela@redhat.com>
Cc: Kevin Wolf <kwolf@redhat.com>, armbru@redhat.com, qemu-devel@nongnu.org, Luiz Capitulino <lcapitulino@redhat.com>

Juan Quintela wrote:
> Luiz Capitulino <lcapitulino@redhat.com> wrote:
> > On Wed, 21 Apr 2010 15:28:16 +0200
> > Kevin Wolf <kwolf@redhat.com> wrote:
> I tried a variation of this in the past, and was not a clear agreement.
> 
> Basically, after a working migration to other host, you don't want to
> allow "cont" on the source node (it target has ever changed anything, it
> would give disk corruption).

This is not true if the target is using a copy of the disk.

Making copies is cheap on some hosts (Linux btrfs with it's COW features).

Forking a guest can be handy for testing things, starting from a known
run state.  The only thing to get confused is networking because of
duplicate addresses, and there are host-side ways around that (Linux
network namespaces).

If I understand correctly, we can already do this by migrating to a
file and copying the files.  There's no reason to block the live
equivalent, provided there is a way to copy the disk image when it's
quiesced.

So it's wrong to block "cont" on the source, but 
"cont --I_know_what_I_am_doing" might be good advice :-)

> But my suggestion to disable "cont" after that got complains that people
> wanted a "I_know_what_I_am_doing_cont". (not the real syntax).  Perhaps
> it is time to revise this issue?

-- Jamie