From mboxrd@z Thu Jan  1 00:00:00 1970
Received: from eggs.gnu.org ([2001:4830:134:3::10]:47948)
	by lists.gnu.org with esmtp (Exim 4.71)
	(envelope-from <kraxel@redhat.com>) id 1VGpNq-0007Bm-GU
	for qemu-devel@nongnu.org; Tue, 03 Sep 2013 08:07:04 -0400
Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71)
	(envelope-from <kraxel@redhat.com>) id 1VGpNg-0007Aa-O4
	for qemu-devel@nongnu.org; Tue, 03 Sep 2013 08:06:58 -0400
Received: from mx1.redhat.com ([209.132.183.28]:27237)
	by eggs.gnu.org with esmtp (Exim 4.71)
	(envelope-from <kraxel@redhat.com>) id 1VGpNg-0007AT-Gk
	for qemu-devel@nongnu.org; Tue, 03 Sep 2013 08:06:48 -0400
Received: from int-mx09.intmail.prod.int.phx2.redhat.com
	(int-mx09.intmail.prod.int.phx2.redhat.com [10.5.11.22])
	by mx1.redhat.com (8.14.4/8.14.4) with ESMTP id r83C6lKL026177
	(version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK)
	for <qemu-devel@nongnu.org>; Tue, 3 Sep 2013 08:06:47 -0400
Message-ID: <1378210004.3618.40.camel@nilsson.home.kraxel.org>
From: Gerd Hoffmann <kraxel@redhat.com>
Date: Tue, 03 Sep 2013 14:06:44 +0200
In-Reply-To: <20130903093231.GD32024@redhat.com>
References: <1378114724-1748-1-git-send-email-gren@redhat.com>
	<1378114724-1748-4-git-send-email-gren@redhat.com>
	<20130902125757.GH15704@redhat.com>
	<1378194712.3618.12.camel@nilsson.home.kraxel.org>
	<20130903093231.GD32024@redhat.com>
Content-Type: text/plain; charset="UTF-8"
Mime-Version: 1.0
Content-Transfer-Encoding: 7bit
Subject: Re: [Qemu-devel] [libvirt] [PATCH 3/5] qemu: add usb-bot support
 from disks points of view
List-Id: <qemu-devel.nongnu.org>
List-Unsubscribe: <https://lists.nongnu.org/mailman/options/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=unsubscribe>
List-Archive: <http://lists.nongnu.org/archive/html/qemu-devel>
List-Post: <mailto:qemu-devel@nongnu.org>
List-Help: <mailto:qemu-devel-request@nongnu.org?subject=help>
List-Subscribe: <https://lists.nongnu.org/mailman/listinfo/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=subscribe>
To: "Daniel P. Berrange" <berrange@redhat.com>
Cc: libvir-list@redhat.com, Guannan Ren <gren@redhat.com>, qemu-devel@nongnu.org

  Hi,

> > > How does this work if we start off a guest with 3 disks
> > > attached to the usb-bot SCSI controller. Then hot-unplug
> > > the 2nd disk.
> > 
> > You can't hotplug individual luns anyway.
> 
> How does hotplug/unplug work in the context of usb-bot ?
> 
> AFAIK we need to be able to run
> 
>   device_add usb_bot
>   drive_add file...
>   device_add scsi-hd
> 
> And the reverse, to unplug it, if we're to have feature parity with
> usb-storage.

Hot-unplug is easy.  You can remove the usb-bot device which will also
remove all child devices.

Hot-plug doesn't work at the moment, and I don't see any obvious way to
fix that properly :-(

We need some way to hotplug a *group* of devices (usb-bot + all
children) as usb-bot itself is hotpluggable but the individual scsi
devices connected to it are not.

I could allow hotplug on usb-bot as workaround, then you can do

  stop
  device_add usb_bot
  device_add scsi-{hd,cd,whatever}
  cont

but that would be more a gross hack than a solution ...

cheers,
  Gerd