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Re: [Xen-devel] PATCH: Fix name uniqueness check

To: Jim Fehlig <jfehlig@xxxxxxxxxx>
Subject: Re: [Xen-devel] PATCH: Fix name uniqueness check
From: "Daniel P. Berrange" <berrange@xxxxxxxxxx>
Date: Thu, 27 Sep 2007 18:39:15 +0100
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On Thu, Sep 27, 2007 at 11:16:27AM -0600, Jim Fehlig wrote:
> Daniel P. Berrange wrote:
> > Changeset  15124:f5459c358575 altered check_name() in XendDomainInfo so that
> > it compares domain IDs instead of UUIDs. This breaks a number of things
> >
> >  - You can no longer use 'xm new' to define a persistent config file for
> >    a running guest. This breaks the key OS provisioning scenario where
> >    you boot a kenrel+initrd for the installer, and at the same time define
> >    a permanent config with pygrub.
> >
> >  - It lets you define multiple inactive guests with different UUIDs, but  
> >    the same name because all inactive guests have a domid of None. So you
> >    can now end up with multiple guests with same name, which is contrary
> >    to the goal implied by the patch which was name uniqueness.
> >
> > It is unclear from the original commit logs just what scenario it was trying
> > to protect against, but the original checking of uniqueness based on UUID 
> > was correct & is what was used in previous releases XenD.
> >   
> Yes, I was not sure what this patch was attempting to fix either.  There
> was some discussion about the patch in this thread
> http://lists.xensource.com/archives/html/xen-devel/2007-05/msg00887.html

Ok, so if I follow that correctly, the crux of the issue is that it was 
possible to start 2 unmanaged domains with same name and same uuid. So
I think we can probably address that by checking for UUID, and the only
if both are running, also check for domid match. So really a combo of
both the original & current code.

> At any rate, the patch was giving me some problems with reboot so I
> added to the misery with this
> http://xenbits2.xensource.com/xen-unstable.hg?rev/9f4f70233041

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