From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from [140.186.70.92] (port=56315 helo=eggs.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1OOWNY-0005LK-7G for qemu-devel@nongnu.org; Tue, 15 Jun 2010 09:40:41 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.69) (envelope-from ) id 1OOWN9-0008TS-9z for qemu-devel@nongnu.org; Tue, 15 Jun 2010 09:40:12 -0400 Received: from mx1.redhat.com ([209.132.183.28]:46194) by eggs.gnu.org with esmtp (Exim 4.69) (envelope-from ) id 1OOWN9-0008TI-03 for qemu-devel@nongnu.org; Tue, 15 Jun 2010 09:40:11 -0400 Received: from int-mx03.intmail.prod.int.phx2.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.16]) by mx1.redhat.com (8.13.8/8.13.8) with ESMTP id o5FDe9jK004632 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK) for ; Tue, 15 Jun 2010 09:40:10 -0400 Received: from cleopatra.tlv.redhat.com (cleopatra.tlv.redhat.com [10.35.255.11]) by int-mx03.intmail.prod.int.phx2.redhat.com (8.13.8/8.13.8) with ESMTP id o5FDe8o4016926 for ; Tue, 15 Jun 2010 09:40:09 -0400 Message-ID: <4C1782B8.6050602@redhat.com> Date: Tue, 15 Jun 2010 16:40:08 +0300 From: Avi Kivity MIME-Version: 1.0 Subject: Re: [Qemu-devel] RFC v2: blockdev_add & friends, brief rationale, QMP docs References: <4C17420E.40601@redhat.com> <4C177581.2040106@redhat.com> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Markus Armbruster Cc: Kevin Wolf , Christoph Hellwig , Gerd Hoffmann , qemu-devel@nongnu.org, Luiz Capitulino On 06/15/2010 04:27 PM, Markus Armbruster wrote: > >> I'm only talking about the interface, not the implementation. >> Internal design details shouldn't be exposed. >> >> For the implementation, I imagine you can create an empty blockdev >> during guest device creation and treat blockdev_add/blockdev_del as >> media change/eject. >> > If blockdev_del only ejects media, then we need another command to get > rid of a blockdev. > No. If you have a blockdev just to satisfy the guest device's need for a blockdev pointer, you can delete it automatically when the last reference goes. > Unless you propose that blockdev_del merely ejects media if the blockdev > is being used by a device, but destroys the blockdev outright if not. > But that would be sick, wouldn't it? > Create a blockdev implicitly with guest device creation, and use blockdev_add (or media_attach) to attach the media. (but that creates a window where the guest device is visible but media is not yet inserted?) >>>> To pretend you're a media changer, blockdev_add all your cds at once >>>> and just change the guest/host association when you want to hear a new >>>> band. >>>> >>>> For a fake a multipath setup, blockdev_add one device, associate it >>>> with multiple guest interfaces. >>>> >>>> Otherwise, looks good. >>>> >>>> >>> Any preference on the command line option syntax? >>> >>> >> Something incredibly long and complicated? >> >> We might keep the existing stuff which is already complicated enough >> for users, and ask machines to build guests using QMP instead of the >> command line. >> > I sketched three ways to do -blockdev. They attempt to make the simple > simple, and the complex possible. Any preference among them? > > I'll look again. > We can't simply keep -drive, because of the flaws I listed in the > rationale. > Ok. -- error compiling committee.c: too many arguments to function