From mboxrd@z Thu Jan 1 00:00:00 1970 From: Wei Liu Subject: Re: [RFC] support more qdisk types Date: Tue, 2 Feb 2016 14:59:30 +0000 Message-ID: <20160202145930.GB25660@citrix.com> References: <56A6BCDE.6040900@suse.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline In-Reply-To: <56A6BCDE.6040900@suse.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Jim Fehlig Cc: Ian Jackson , Ken Johnson , Wei Liu , Ian Campbell , xen-devel List-Id: xen-devel@lists.xenproject.org On Mon, Jan 25, 2016 at 05:25:02PM -0700, Jim Fehlig wrote: > I would like to hear the community's opinion on supporting more qdisk types in > xl/libxl, e.g. nbd, rbd, iSCSI, etc. I prefer supporting additional qdisk types > in libxl over apps like xl or libvirt doing all the setup, producing a block > device, and then passing that to libxl. Each libxl app would have to > re-implement functionality already provided by qdisk. libxl already supports > IDE, AHCI, SCSI, and Xen PV qdisks. My suggestion is to extend that to initially > include nbd, rbd, and iSCSI. Sheepdog, ssh, etc. could be added in the future. > This is a good idea in general. > I considered several approaches to supporting additional qdisk types, based > primarily on changes to the disk cfg and interface. At one extreme is to change > nothing and use the existing 'target=' to encode all required config for the > additional qdisk types. libxl would need to be taught how to turn the blob into > an appropriate qdisk. I think you mean "libxlu would need to be taught how to turn that blob into an appropriate libxl_device_disk" -- libxl doesn't parse user configuration, it deals with the libxl_device_disk directly to construct arguments for QEMU. Either it is done by extending target= or adding discrete options, the heavy lifting is going to be in libxlu. I don't think we want to parse a string inside libxl. > At the other extreme is extending xl-disk-configuration > with discrete knobs for each possible config item and making the > libxl_device_disk structure more hierarchical. E.g. > I don't think the second half (hierarchical structure) is closely tied to whether target= is extended or discrete knobs are used. And extending the structure seems to be the right thing to do. Wei.