[libvirt] [PATCH alt] conf: Allow user define their own alias
Daniel P. Berrange
berrange at redhat.com
Tue Oct 3 14:19:02 UTC 2017
On Fri, Sep 29, 2017 at 09:06:01AM +0200, Michal Privoznik wrote:
> It comes handy for management application to be able to have a
> per-device label so that it can uniquely identify devices it
> cares about. The advantage of this approach is that we don't have
> to generate aliases at define time (non trivial amount of work
> and problems). The only thing we do is parse the user supplied
> tag and format it back. For instance:
> <disk type='block' device='disk'>
> <driver name='qemu' type='raw'/>
> <source dev='/dev/HostVG/QEMUGuest1'/>
> <target dev='hda' bus='ide'/>
> <alias user='myDisk0'/>
> <address type='drive' controller='0' bus='0' target='0' unit='0'/>
> Signed-off-by: Michal Privoznik <mprivozn at redhat.com>
> An alternative approach to:
> Honestly, I prefer this one as it's simpler and we don't have to care about
> devices changing their aliases on cold plug. I mean, on cold (un-)plug we'd
> have to regenerate the aliases so it might be hard to track certain device.
> But with this approach, it's no problem.
Can you elaborate on you mean by the cold plug problem here ?
Are you saying that if you cold plug a single device, we would regenerate
aliases on every single other device too ? I would surely think we can
avoid that kind of thing.
To make hotplug easier for applications we could add a V2 hotplug API
which *returns* the fully-expanded device XML.
That way applications would immediately learn the alias of the newly
hotplugged device in a simple manner.
While we were at it, this would give us opportunity to make the v2
hotplug API support hotplugging of multiple devices at once. This is
a feature we've needed for PCI assignment where some devices have to
be co-assigned at the same time.
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