[Libvir] [PATCH] add bootloader_args to libvirt xml to support bootloaders (like pypxeboot for example) that require arguments
veillard at redhat.com
Thu Jun 7 14:08:20 UTC 2007
On Tue, Jun 05, 2007 at 08:55:34AM -0400, Daniel Veillard wrote:
> On Tue, Jun 05, 2007 at 08:35:21AM -0400, Hugh Brock wrote:
> > Daniel Veillard wrote:
> > > This all looks simple and clear except one point.
> > >We used to process pygrub differently than other bootloaders, basically
> > >testing
> > >for that value and making it a special case, ending up with 3 different
> > >case:
> > > - no bootloader (bootloader == 0)
> > > - bootloader is not pygrub (bootloader == 1)
> > > - bootloader is pygrub (bootloader == 2)
> > >I'm pretty sure we made that on purpose to avoid some problem, but I can't
> > >remember why :-(. Your patch changes that and gets back to only 2 case, and
> > >I don't see an explanation of what changed to drop the special case. Can
> > >you explain why this was changed ? I also wonder what would happen if we
> > >drop
> > >the new libvirt resulting from this say on a Fedora Core 6, would that
> > >break
> > >pygrub in that environment due to the change ?
> > So this is an interesting question, and you may well be right that I
> > have removed some special case that was at some point (or is still)
> > important. Here is the full story as I understand it. In the old code,
> > both the no-bootloader case (bootloader=0) and the non-pygrub case
> > (bootloader=1) allow <kernel> and <initrd> in the xml along with the
> > <bootloader> element. pygrub takes no such arguments, so if that was the
> > bootloader being used (bootloader=2) the <kernel> and <initrd> were
> > omitted.
> > As you can imagine when I saw this code my first thought was "what the
> > hell is this" <g>, so I checked with Dan. We were both unable to imagine
> > a scenario in which having <kernel> and <initrd> in the xml along with
> > <bootloader> was useful, since if you know what kernel and initrd you
> > want to boot (for the paravirt case, of course), you don't need a
> > bootloader. We also didn't much like having a check for "pygrub"
> > hardcoded in libvirt, especially since I would have had to extend it to
> > be "pygrub" || "pypxeboot" (yuck).
> > If we really do need this special case then I'm more than happy to put
> > it (or some less nasty version of it) back. I agree that it does have
> > the look of something that was added for a specific edge case.
> I remember the 'yuck but I don't see any other way' feeling when we
> added this. But since 1/ I can't remember precisely 2/ you and Dan looked
> at it and couldn't find either, I'm fine taking the very small risk of breaking
> something in an older release. Libvirt is by essence a place where nasty
> tricks like this will pile over time, and while we really try to keep
> compatibility, if really we can find/remember why one could be needed
> cleanup makes sense.
> Let's apply the patch then ! Will do shortly unless you disagree,
Red Hat Virtualization group http://redhat.com/virtualization/
Daniel Veillard | virtualization library http://libvirt.org/
veillard at redhat.com | libxml GNOME XML XSLT toolkit http://xmlsoft.org/
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