From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from [140.186.70.92] (port=37738 helo=eggs.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1OntoU-0000vk-TG for qemu-devel@nongnu.org; Tue, 24 Aug 2010 09:45:20 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.69) (envelope-from ) id 1OntoM-0003I5-OZ for qemu-devel@nongnu.org; Tue, 24 Aug 2010 09:45:18 -0400 Received: from mx1.redhat.com ([209.132.183.28]:5552) by eggs.gnu.org with esmtp (Exim 4.69) (envelope-from ) id 1OntoM-0003Hq-ID for qemu-devel@nongnu.org; Tue, 24 Aug 2010 09:45:10 -0400 Date: Tue, 24 Aug 2010 14:44:46 +0100 From: "Daniel P. Berrange" Subject: Re: [Qemu-devel] [PATCH 4/5] Add generic drive hotplugging Message-ID: <20100824134446.GM7376@redhat.com> 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> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4C73CBC9.4050602@suse.de> Reply-To: "Daniel P. Berrange" List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Alexander Graf Cc: Markus Armbruster , Luiz Capitulino , qemu-devel List , Aurelien Jarno , Gerd Hoffmann 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: > > > >> Daniel P. Berrange wrote: > >> > >>> On Tue, Aug 24, 2010 at 12:02:30AM +0200, Alexander Graf wrote: > >>> > >>> > >>>> The monitor command for hotplugging is in i386 specific code. This is just > >>>> plain wrong, as S390 just learned how to do hotplugging too and needs to > >>>> get drives for that. > >>>> > >>>> So let's add a generic copy to generic code that handles drive_add in a > >>>> way that doesn't have pci dependencies. > >>>> > >>>> I'm not fully happy with the patch as is. IMHO there should only be a > >>>> single target agnostic drive_hot_add function available. How we could > >>>> potentially fit IF_SCSI in there I don't know though. > >>>> > >>>> > >>> I'm not sure that this patch is actually neccessary. Via a undocumented, > >>> sick, dirty hack, you can already use the current drive_add command > >>> without a PCI address, for both virtio + scsi. In fact not using the > >>> PCI address with drive_add is the preferred approach in the new qdev > >>> world even on x86 > >>> > >>> > >> It is certainly necessary since the current code is in a big fat #if > >> defined(TARGET_I386) block :). > >> > > > > True, true, killing the #ifdef is needed :-) > > > > And moving it out of the pci specific file. Yeah :). Basically my > proposal was to take the patches as is and phase out the pci-hotplug.c > version. > > > > >>> 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. Regards, Daniel -- |: Red Hat, Engineering, London -o- http://people.redhat.com/berrange/ :| |: http://libvirt.org -o- http://virt-manager.org -o- http://deltacloud.org :| |: http://autobuild.org -o- http://search.cpan.org/~danberr/ :| |: GnuPG: 7D3B9505 -o- F3C9 553F A1DA 4AC2 5648 23C1 B3DF F742 7D3B 9505 :|