Re: [Qemu-devel] Should we auto-generate IDs?

[Eric Blake <eblake@redhat.com>]

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On 08/27/2015 07:51 AM, Daniel P. Berrange wrote:
> On Thu, Aug 27, 2015 at 09:39:10AM -0400, Programmingkid wrote:
>>
>>> Better still might be fixing things to where we add a global command
>>> line option that outright fails any attempt to create an unnamed object.
>>> The option would be off by default for back-compat.  But management
>>> apps like libvirt can turn it on once they are prepared to name every
>>> object they create (which in turn may imply fixing any remaining
>>> interfaces that cannot name an object to add in that ability for
>>> management to pass in a name).  Then there would be no unnamed objects,
>>> no ambiguity, and no need to generate names.
>>
>> I do agree with giving every device an ID, but I don't think failing if the user
>> forgets to give one is necessary. If libvirt doesn't give devices and ID, it
>> would probably benefit from having QEMU do it for libvirt.

No, you're misunderstanding our argument. The moment there is more than
one device with an auto-assigned name is the moment that management
doesn't know which device got which name, so it's better for management
to pick a name in the first place.

> 
> Libvirt always gives an explicit ID.

Except it doesn't, yet.  Libvirt still needs to be taught to name all
node devices (and I'm slowly trying to work on patches towards that goal).

>     It is impossible to rely on QEMU
> assigning IDs, because there is no reliable way to identify what ID
> QEMU assigned to each device after the fact. Other management apps
> would have the same problem, so auto-generated IDs are pretty useless
> in that respect.

It's not to say that auto-generated names would be useless when running
qemu manually from the command line, but I agree that management
probably can't safely rely on auto-generated names, and therefore
solving the issue of auto-generating names is less important.

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org


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