[Xen-devel] Deficiencies in guest bootloader design

["Michael Paesold" <mpaesold@xxxxxx>]

I have tried to use a dynamically activated block device with pygrub 
(actually drbd, but could be enbd, nbd, or simply any vbd other than phy: or 
file:). That does not work.
The problem is that the bootloader is not called from Xend, after virtual 
block devices are setup, but instead it is called directly from xm, i.e. in 
xm/create.py.
If I have looked correctly, (1) a bootloader cannot be used for devices such 
as nbd: or enbd: devices, and (2) a bootloader cannot be used when accessing 
Xend via XML-RPC (or libvirt or similar), because the whole notion of a 
"bootloader" at domain creation time is only available in "xm", but not in 
Xend.
It should be fixable, since at least on guest *restart*, 
xend/XendDomainInfo.py already uses the bootloader to re-extract the kernel 
image from the vbd.
Is there anyone working on bootloader improvements? If not, is a change to 
move the bootloader stuff from xm to Xend acceptable? In that case I could 
try to come up with a patch.
There are some issues though. In XendDomainInfo.initDomain, image.create is 
done before self.createDevices. Can this be changed easily?
Thanks for any help or guidance.

Best Regards,
Michael Paesold 


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