Re: [Xen-devel] questions about adding MP support to gdbserver

[Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>]

>  Why doesn't GETDOMAININFO return a bitmask of online vcpus? It looks 
> as if the only way to find out what vcpus are online is to iterate 
> through, up to maxvcpuid.
Yes, that's the correct approach.

>  Do GETVCPUINFO and GETVCPUCONTEXT take vcpuids? In other words, if I 
> have 4 cpus online I do a get call on 3, down 2, then do a get call on 
> 3 again, will I get the same result?
Yes.

>  Where is an example of userspace code iterating through the online 
> vcpus?
> http://lists.xensource.com/xen-devel
There are examples in xenstat, but it uses its own interface library 
(not libxenctrl) so it will probably only confuse. You have the right 
approach described above anyway:
 1. getdomaininfo
 2. for (i = 0; i <= info.max_vcpu_id; i++)
 3.     getvcpuinfo / getvcpucontext
 4.     info.online tells you whether the vcpu is up or down
 5.     either way, getvcpucontext will succeed if the domU has booted 
that vcpu
 -- Keir


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