Hello Kiri,
Am Montag 31 Oktober 2011 15:15:12 schrieb Jiri Denemark:
> Is there any way you can pass the exact order to Xen?
Not that I know of. This is one of the corner cases, which is only relevant if
you have a Xen-PV domain AND are using PyGrub as the boot-loader. For HV the
flag is unused and for direct kernel boot you don't need it either. Only for
PV+bootloader needs Xend a way to find the disk containing the kernel.
In xen-4.1/tools/python/xen/xend/XendDomainInfo.py:3234 _configureBootloader()
build a list of all vbds marked bootable and passes only the first one to
Pygrub. Technically you mark multiple disks as bootable, but the flag is only
set in xen-4.1/tools/python/xen/xend/XendConfig.py:1498 device_add(), which
does this exactly once for the first disk added.
> Multiple devices with
> bootIndex are allowed (the indexes are unique of course) to specify booting
> preference and by setting (bootable 1) anytime bootIndex != 0 makes all
> such devices bootable in unspecified order.
Same with Xen — I thinks: If you mark multiple disks as bootable, the first
disk gets used — whichever that is.
> If only one bootable device is
> supported by Xen, you should probably emit (bootable 1) only for bootIndex
> = 1 and maybe even forbid more than one device with bootIndex.
This makes perfect sense for libvirt → xen, since we want determinictic
behaviour.
But if multiple disk are marked bootable, converting xen → libvirtd either has
to pick one disk and report just that disk as bootable; or reports all disks
marked as bootable.
Either way, round-trip is broken. I wish XenLight would be useable.
> You also need to add 'deviceboot' feature to guest capabilities XML so that
> apps know they can use <boot order='n'/> when creating this kind of guests.
Will have a look.
Sincerely
Philipp
--
Philipp Hahn Open Source Software Engineer hahn@xxxxxxxxxxxxx
Univention GmbH Linux for Your Business fon: +49 421 22 232- 0
Mary-Somerville-Str.1 D-28359 Bremen fax: +49 421 22 232-99
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