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Re: [Xen-devel] [PATCH 3/3] x86_64: allow more vCPU-s per guest



>>> Keir Fraser <keir.fraser@xxxxxxxxxxxxx> 18.06.09 11:16 >>>
>On 10/06/2009 15:48, "Jan Beulich" <JBeulich@xxxxxxxxxx> wrote:
>
>> Since the shared info layout is fixed, guests are required to use
>> VCPUOP_register_vcpu_info prior to booting any vCPU beyond the
>> traditional limit of 32.
>
>Applied. Is the vcpu[] array re-allocation in XEN_DOMCTL_max_vcpus an
>example of over-optimistic-concurrency-control? It can't really be 100% safe
>without extra locking on all users of that array (not good), or using rcu
>(better), can it. The wmb() is a nice try. ;-)

Agreed. Originally I intended to add at least a comment, but after realizing
that the path currently is only reached during domain creation (and I believe
there are issues elsewhere if one would really allow increasing the # of
vCPU-s in a domain on the fly), I decided to leave it as is (and the wmb()
can be considered sort of a comment to that effect).

Jan


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