From mboxrd@z Thu Jan  1 00:00:00 1970
From: "Chen, Tiejun" <tiejun.chen@intel.com>
Subject: Re: [v10][PATCH 11/16] tools/libxl: detect and avoid
 conflicts with RDM
Date: Tue, 21 Jul 2015 21:41:38 +0800
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To: Ian Jackson <Ian.Jackson@eu.citrix.com>
Cc: Stefano Stabellini <stefano.stabellini@eu.citrix.com>, Wei Liu <wei.liu2@citrix.com>, Ian Campbell <ian.campbell@citrix.com>, xen-devel@lists.xen.org
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>>> But another answer would be to take the union of the specified
>>> regions.  That would be more complicated, because the union would have
>>> to be computed.
>>>
>>>>                if (d_config->rdms[i].start == rdm_start)
>>>>                    return;
>>>
>>> That doesn't, of course, compute the union.
>>
>> Sorry I don't understand what the "take the union of the specified
>> regions" is here.
>
> A "region" is a subset of the address space.  I meant the set union:
>    https://en.wikipedia.org/wiki/Union_%28set_theory%29
>
> That is, an address would be reserved if it was reserved in any of the
> rdm regions implied by the config.

Are you saying this point?

"The union of two sets A and B is the set of elements which are in A, in 
B, or in both A and B."

>
> The explicitly specified regions might overlap with the computed ones,
> without being identical. Computing the union would not be entirely
> trivial.
>

Just to your example,

   libxl_domain_config cfg;
   cfg.stuff = blah;
   cfg.rdm.strategy = HOST;

   libxl_domain_create_new(&cfg, &domid);
   libxl_domain_destroy(domid);

Here looks you mean d_config->rdms would be changed, right? Currently 
this shouldn't be allowed. But I think we need to further discussion 
make this case clear after feature freeze since we didn't have this kind 
of assumption in our previous design.

   libxl_domain_create_new(&cfg, &domid);

Thanks
Tiejun