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Re: [Xen-devel] xl list -l doesn't work for incoming domain



On Mon, Nov 10, 2014 at 10:01:22AM -0500, Zhigang Wang wrote:
> On 11/10/2014 07:35 AM, Wei Liu wrote:
> > I see. At that point the configuration was not available, yet. After the
> > domain is successfully migrated, the configuration should be available.
> > 
> > I think a domain under construction without domain configuration is a
> > valid state. What do you think?
> 
> Here is my thought:
> 
> 1. In this design, if I watch xenstore @introduceDomain, it will not been
>    triggered until migration finish.
> 

OK. What in this design makes behavior different than before? Are you
suggesting "xl list -l" has something to do with your xenstore watch? I
don't think I can get this.

My guess is that, you have some tool that watches @introduceDomain,
which happens *before* the domain creation is finished. And your tool
needs to get domain information once your watch fires.  Here with this
design, your tool cannot get the correct information until migration is
finished. Am I right?

However, in previous design, even if you manage to get configuration
before migration is finished, I don't think that configuration reflects
the true configuration of that domain. It's conceptually bogus.

In any case, if you look at xenstore code, XS_INTRODUCE doesn't mean a
domain is started, so using it for that purpose would be wrong.

> 2. Because we have multiple places (hypervisor, xenstore, /var/lib/xen) 
> holding
>    domain state, we need to define what does it mean by "VM started".
> 

If my above analysis is correct, will some kind of @startDomain event solve
your problem?

But this involves making changes to Xenstore protocol. Let's not go into
details until we make sure your requirement is well understood.

Wei.

> 3. It looks like a inconsistent state and we may want to eliminate or keep
>    it as short as possible.
> 
> Thanks,
> 
> Zhigang

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