Re: [libvirt] [Xen-devel] [PATCH] libxl: allow an <emulator> to be selected in the domain config XML

On Fri, 2013-05-31 at 12:46 +0200, Marek Marczykowski wrote: > On 31.05.2013 10:25, Ian Campbell wrote: >> On Thu, 2013-05-30 at 11:53 -0600, Jim Fehlig wrote: >>> Marek Marczykowski wrote: >>>> On 01.05.2013 16:11, Daniel P. Berrange wrote: >>>> >>>>> On Wed, May 01, 2013 at 02:44:11PM +0100, David Scott wrote: >>>>> >>>>>> On 01/05/13 09:46, Ian Campbell wrote: >>>>>> >>>>>>> I would suggest that libvirt+libxl expose the version as the "emulator" >>>>>>> option and not the path. Just leave the path as the default in the >>>>>>> normal case. You may also want to provide an extra >>>>>>> emulator-path-override tag/attribute/XML for advanced users, but that's >>>>>>> up to you. >>>>>>> >>>>>>> If you need to support upgrade from xend then you could perhaps treat >>>>>>> <emulator> values not in the set of valid LIBXL_DEVICE_MODEL_VERSION >>>>>>> string (currently "qemu-xen" and "qemu-xen-traditional") as a path to a >>>>>>> qemu-xen-traditional device model -- no xend user can possibly have been >>>>>>> using the new device model with xend. Or you could take the approach >>>>>>> that xl does and just warn. >>>>>>> >>>>>> This would work for me: it doesn't seem too bad to consider >>>>>> "qemu-xen" and "qemu-xen-traditional" as special virtual paths. It's >>>>>> a useful observation that xend never supported the new device model. >>>>>> Jim: should I cook up patch v3? :-) >>>>>> >>>>> No, that really doesn't fly. The <emlator> element must always point >>>>> to a qualfied binary path. >>>>> >>>>> IMHO, libvirt should just default to the new QEMU binary and if people >>>>> want to use the old one, they can configure the emulator path for it. >>>>> >>>> >>>> What about stubdom? Any idea how to do it better than special paths? Even if >>>> given path will point to stubdom binary, I don't know how libvirt shoud >>>> distinguish it from standalone qemu and set b_info->device_model_stubdomain >>>> accordingly. >>>> >>> >>> As mentioned in my reply to your stubdom patch, this should be handled >>> in libxl IMO. >> >> The default is handled in libxl, so you don't need to do anything if you >> don't want to. It's up to you if you want to provide an override >> facility in libvirt. Personally I'd do it with a specific XML >> property/key/whatever rather than magic emulator paths... > > Optional attribute for <emulator> tag? Maybe sth like: > <emulator type="stubdom">/usr/lib/xen/boot/ioemu-stubdom.gz</emulator> > ? FWIW the path can be omitted and libxl will DTRT.