On Sun, Oct 29, 2017 at 08:39:08PM -0600, Jim Fehlig wrote:
Hi All,
It may be a foolish en devour, but I'm trying to make a qemu hook script
that provides the semantics of an old, custom xen block script. The script
parses <disk> info, does some setup based on that, and then rewrites part of
the config based on results of the setup. As an example, here is an XML
snippet of a <disk> device on input to the hook script
<disk type='block' device='disk'>
<driver name='qemu' type='raw'/>
<source dev='some-dev-config'/>
<target dev='vdb' bus='virtio'/>
</disk>
and XML returned by the script
<disk type='block' device='disk'>
<driver name='qemu' type='raw'/>
<source dev='/dev/foo'/>
<target dev='vdb' bus='virtio'/>
</disk>
The hook script performs the setup and substitution in the "prepare" phase,
but I noticed the results are never used when subsequently starting the
domain. Indeed qemuProcessStartHook passes a NULL buffer to virHookCall, so
the output XML of the hook is never collected. Does anyone have objections
to using the XML returned from the "prepare" and "release" hook
script
phases, similar to how it is used in the "restore" and "migrate"
phases?
That was an explicit decision - we don't want hook scripts arbitrarily
modifying the XML during startup. They're there to let you trigger
external actions, but they're not there to let you modify the config.
Regards,
Daniel
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