From mboxrd@z Thu Jan  1 00:00:00 1970
From: "Michael S. Tsirkin" <mst@redhat.com>
Subject: Re: [PATCH 0/5] vhost-scsi: Add support for host virtualized target
Date: Mon, 28 Jan 2013 15:36:09 +0200
Message-ID: <20130128133609.GB15108@redhat.com>
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To: Paolo Bonzini <pbonzini@redhat.com>
Cc: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>, kvm-devel <kvm@vger.kernel.org>, Jan Kiszka <jan.kiszka@siemens.com>, qemu-devel <qemu-devel@nongnu.org>, Zhi Yong Wu <wuzhy@cn.ibm.com>, Anthony Liguori <aliguori@linux.vnet.ibm.com>, target-devel <target-devel@vger.kernel.org>, lf-virt <virtualization@lists.linux-foundation.org>, Christoph Hellwig <hch@lst.de>
List-Id: virtualization@lists.linuxfoundation.org

On Mon, Jan 28, 2013 at 02:29:23PM +0100, Paolo Bonzini wrote:
> Il 28/01/2013 14:11, Michael S. Tsirkin ha scritto:
> > > I asked for a standalone device because the configuration mechanism
> > > (configfs vs. command-line) and the feature set are completely
> > > different.  Unlike virtio-net, it's not possible to switch one to the
> > > other at run time.
> > 
> > Exactly the same applies to any other frontend option.
> > For example if you have two qemu instances with
> > different num_queues values you can not migrate one
> > to the other.
> > So in this sense it is not different from any other
> > frontend option, right?
> 
> Indeed, in this sense it is not.
> 
> Actually in this case migrating one to the other could succeed, and make
> all disks disappear on the destination (because of the different
> configuration mechanism).  That however could be overcome with vhost=on
> registering a migration blocker.

Or better add a subsection if vhost is set: vhost=on to vhost=on
can migrate, right?

> I won't really block the patch with the vhost=on/off frontend option if
> it is properly done (e.g. the QEMU SCSI bus should not be created for
> vhost=on) and minimally invasive to the non-vhost code.
> 
> Paolo