Re: [Libvir] Fix handling of HVM boot parameters

Jeremy mentioned that it looked like libvirt wasn't able to create an HVM domain configured to boot off cdrom, so I took a closer look at the code and indeed the code dealing with <boot> section was both incomplete, and just plain broken. Incomplete in so much as it never included details of the ISO file backing the CDROM, and broken in so much as it was doing string comparisons against the wrong variables. Digging further found lots more work relating to creation of HVM domains so I've had a go at writing a patch to resolve matters. * Parsing of UUID from SEXPR assumed that the UUID fetched would always have four '-' in the usual places. Well, when you run 'dumpxml' from virsh the <uuid> element has the UUID encoded without any '-' chars. If you feed this back into 'virsh create' and then once again run 'dumpxml' parsing will fail & libvirt throws errors. So this patch allows for parsing of UUID's without '-'. * The XML document size was limited to 1k - we just 'malloc(1000)'. While this was enough for common cases, if someone creates lots of disk or network devices this would overflow and libvirt return an error. So I increased it to 4k which ought to be enough for forseeable future - in any case my previous patch to fetch XML via the proxy is limited to 4k in size too. Now onto the fine details... When converting SEXPR into XML current code is doing the following: (boot a) -> <boot dev='/dev/fd0'/> (boot c) -> <boot dev='hda'/> (boot d) -> <boot dev='/dev/cdrom'/> This is rather inconsistent - the 'hda' is intended to map to an entry in <devices> block. The '/dev/fd0' and '/dev/cdrom' entries did not map to anything. Meanwhile, when converting from XML to SXEXPR it is doing the following <boot dev='hda'/> -> (boot a) <boot dev='hdd'/> -> (boot d) <boot dev='*'/> -> (boot c) Obviously this sucks because these processes should be matching each other. Secondly, the (image (hvm....)) SEXPR has three entries for defining the ISO / disk image file backing the CDROM / Floppy devices. These were just being ignored, rather than turned into <disk> entries within the <devices> block. Similarly there was no way to express a <disk> entry for CDROM/Floppy in the XML when creating a domain. The upshot of all this is that although the last release of libvirt included HVM support it was basically unusable for domain creation unless you were using HD to boot. The XML returned was also incorrect. Now the good news. Since it was sooo broken, we can fix without worrying about XML compatability since there is no way any application could be relying on it in its current state.