From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from [140.186.70.92] (port=37916 helo=eggs.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1OntpS-0001RL-8T for qemu-devel@nongnu.org; Tue, 24 Aug 2010 09:46:19 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.69) (envelope-from ) id 1OntpQ-0003Qc-R0 for qemu-devel@nongnu.org; Tue, 24 Aug 2010 09:46:18 -0400 Received: from cantor.suse.de ([195.135.220.2]:50511 helo=mx1.suse.de) by eggs.gnu.org with esmtp (Exim 4.69) (envelope-from ) id 1OntpQ-0003QR-H1 for qemu-devel@nongnu.org; Tue, 24 Aug 2010 09:46:16 -0400 Message-ID: <4C73CD26.90408@suse.de> Date: Tue, 24 Aug 2010 15:46:14 +0200 From: Alexander Graf MIME-Version: 1.0 Subject: Re: [Qemu-devel] [PATCH 4/5] Add generic drive hotplugging References: <1282600951-30803-1-git-send-email-agraf@suse.de> <1282600951-30803-5-git-send-email-agraf@suse.de> <20100824093155.GB7376@redhat.com> <4C73A2BF.2050605@suse.de> <20100824105154.GH7376@redhat.com> <4C73CBC9.4050602@suse.de> <20100824134446.GM7376@redhat.com> In-Reply-To: <20100824134446.GM7376@redhat.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Daniel P. Berrange" Cc: Markus Armbruster , Luiz Capitulino , qemu-devel List , Aurelien Jarno , Gerd Hoffmann Daniel P. Berrange wrote: > On Tue, Aug 24, 2010 at 03:40:25PM +0200, Alexander Graf wrote: > >> Daniel P. Berrange wrote: >> >>> On Tue, Aug 24, 2010 at 12:45:19PM +0200, Alexander Graf wrote: >>> >>>>> The key is that you should use if=none for all cases. Here are two >>>>> examples of how libvirt does it currently: >>>>> >>>>> VirtIO: >>>>> >>>>> drive_add dummy file=/var/lib/libvirt/images/data.img,if=none,id=drive-virtio-disk1,format=raw >>>>> device_add virtio-blk-pci,bus=pci.0,addr=0x0,drive=drive-virtio-disk1,id=virtio-disk1' >>>>> >>>>> SCSI: >>>>> >>>>> drive_add dummy file=/var/lib/libvirt/images/data.img,if=none,id=drive-scsi0-0-1,format=raw' >>>>> device_add scsi-disk,bus=scsi0.0,scsi-id=1,drive=drive-scsi0-0-1,id=scsi0-0-1 >>>>> >>>>> The 'dummy' value there can be absolutely anything you want. >>>>> It is totaly ignored when QEMU sees if=none in 2nd arg. >>>>> >>>>> >>>>> >>>> I'd be all for removing the pci-hotplug.c version of drive_add then. But >>>> I think the IF_SCSI option there is to append a drive to an existing >>>> SCSI bus, no? >>>> >>>> >>> Actually this SCSI example I give above is appending a drive to an existing >>> bus (scsi0), in slot 1 (scsi-id=1). To best of my knowledge there is no >>> remaining use case that requires use of IF_SCSI, IF_IDE, etc. The IF_NONE >>> approach can cope with all, modulo bugs that appear periodically with code >>> that mistakenly checks for a particular IF_XXX constant. >>> >>> If you wanted to also create a new SCSI bus, before creating the drive on >>> it, you'd need to run three commands in total: >>> >>> device_add lsi,id=scsi0,bus=pci.0,addr=0x7 >>> drive_add dummy file=/var/lib/libvirt/images/data.img,if=none,id=drive-scsi0-0-1,format=raw >>> device_add scsi-disk,bus=scsi0.0,scsi-id=1,drive=drive-scsi0-0-1,id=scsi0-0-1 >>> >>> >> Nice - so we can just deprecate if=!none? >> > > In theory yes, but its not nice to tell users to switch everything over to > use if=none, if we're going to deprecate that too in the next release when > blockdev appears. Might as well just deprecate entire of drive_add/-drive > at once. > I guess I still fail to see the reason for blockdev when we force drive_add to if=none... Alex