Re: [libvirt] xl and libvirt.
On 05/26/2014 08:18 PM, Alvin Starr wrote:
I have been trying do some simulations of an openstack environment on
my
workstation that is running xen and libvirt.
I managed to create nested HVM environments under lx but found a number
of shortfalls in libxl code.
I'm not a libxl user myself, but can at least answer some things:
I have added a nestedhvm as a domain feature and was looking at
inspecting the domain configuration when I realized that the persistant
data is keept in config files in /var/lib/xen/userdata.....
Libvirt and lx have incompatible file names and are using different
config formats.
Libvirt keeps the data as XML and xl keeps them as xm config files.
This means that libvirt domains cannot be manged with xl or xl domains
managed by libvirt.
Part of me thinks that sticking with the XL file format would be nice
from the point of view of being able to use xenlight tools once the
domain is configured.
At the very least it may make sense to keep an XL copy of the config
file in a format that xenlight can use.
Libvirt is a higher layer than xl. The design decision is that if you
use libvirt to manage domains, you should use libvirt syntax (and not xl
syntax), because it makes it easier to translate between libxl or qemu
as your hypervisor all while being used to the common libvirt framework
(in fact, the reason libvirt exists at all is because of xen vs. qemu
issues 7 years ago needing a common wrapper). So libxl should NOT learn
libvirt XML config; but rather, libvirt should have a translation both
into and out of lower-layer config formats.
Such a command already exists, in the form of 'virsh domxml-from-native'
and 'domxml-to-native'; and according to the source code, the libvirt
driver for libxl domains has already supported conversions for the
"xen-xm" and "xen-sxpr" formats since libvirt 0.9.0. If the xl
config
format you are talking about is different than xen-xm or xen-sxpr, then
it's merely a matter of patching
src/libxl/libxl_driver:libxlConnectDomainXML{To,From}Native to
understand a third format. Patches welcome :)
--
Eric Blake eblake redhat com +1-919-301-3266
Libvirt virtualization library http://libvirt.org
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