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Re: [Xen-devel] [PATCH v3 1/7] xen: vNUMA support for PV guests

>>> On 19.11.13 at 15:35, Dario Faggioli <dario.faggioli@xxxxxxxxxx> wrote:
> On mar, 2013-11-19 at 14:01 +0000, Jan Beulich wrote:
>> One thing that I only realized - what information is the guest
>> supposed to use to know the number of virtual nodes it has
>> (needed to size the arrays the handles here point to)?
> If I understand correctly what you're asking, the (current) answer is in
> the Linux patch, here:
> http://bugs.xenproject.org/xen/mid/%3C1384811922-14642-2-git-send-email-ufimt 
> seva@xxxxxxxxx%3E
> which uses num_possible_cpus()
>  http://lxr.linux.no/linux+v3.12/+code=num_possible_cpus 
> to size all the three arrays.

But what guarantees num_possible_cpus() to be larger than some
hypervisor internal variables that the domain has no knowledge
about? Just consider a guest with a Linux configured for just 4
CPUs and 2 nodes, but having a config file specifying 16 vCPU-s on
4 virtual nodes?


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