On 21/10/12 23:49, Dan Kenigsberg wrote:
On Sun, Oct 21, 2012 at 11:57:10AM -0400, Eli Mesika wrote:
----- Original Message -----
From: "Yair Zaslavsky" yzaslavs@redhat.com To: "Livnat Peer" lpeer@redhat.com Cc: "Genadi Chereshnya" gcheresh@redhat.com, engine-devel@ovirt.org, vdsm-devel@fedorahosted.org Sent: Sunday, October 21, 2012 5:38:54 PM Subject: Re: [Engine-devel] unmanaged devices thrown into 'custom' feature
----- Original Message -----
From: "Livnat Peer" lpeer@redhat.com To: "Dan Kenigsberg" danken@redhat.com Cc: "Genadi Chereshnya" gcheresh@redhat.com, engine-devel@ovirt.org, vdsm-devel@fedorahosted.org Sent: Sunday, October 21, 2012 5:18:31 PM Subject: Re: [Engine-devel] unmanaged devices thrown into 'custom' feature
On 21/10/12 16:42, Dan Kenigsberg wrote:
I have just noticed that when a VM is started for the second time, Engine issues the "create" vdsm verb with some information regarding "unmanaged" devices (an example is shown below[1]) in the 'custom' propery bag.
I'm surprised about this, as I was not aware of this usage of the 'custom' dictionary, and Vdsm is not doing anything with the data.
If I recall correctly the idea of passing the unmanaged devices data in the custom property was to enable managing stable device addresses in the hooks (to devices that were added to the VM via hooks from the first place), so this info is there not for VDSM use. For example if you add a device in a hook it will be kept in the engine as a non managed device. later when starting the VM again you would like to assign the same device address to your device, and you can do so because you have access to the original address in the custom properties of the VM.
This is exactly what Eli has explained Gendai and Dan today.
(I was asking here because I did not understand the verbal explanation.)
This is taken from the Stable Device Address design in http://wiki.ovirt.org/wiki/Features/Design/StableDeviceAddresses
Unmanaged Device
Unmanaged Device will be supported in the new format and will include all unhandled devices as sound/controller/etc and future devices. Those devices will be persistent and will have Type , SubType (device specific) and an Address. For 3.1 an unmanaged Device is not exposed to any GUI/REST API. Unmanaged devices are passed to vdsm inside a Custom property. VDSM in it turn is passing this as is for possible hook processing.
Thanks for the elaboration. Too bad that I've missed this issue before.
Are you aware of any hook making use of this? I hope that hook writers are not using APIs that are not documented in vdsmd(8).
It seems as a classic case where a generic bag interface is coerced into an awkward partially-documented interface.
I think that a better approach would have been to pass all devices (managed and unmanaged alike) in the 'devices' property, and let vdsm expose whatever is needed to the before_vm_start hook.
Maybe we can still do this.
That was the original idea but Ayal objected and I think Igor did not like it as well...
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