Xen devel - Jan 2006 - changing max vcpus threshold while a domain is running

Hi Keir,

I am interested in changing the max vcpu threshold for a domain while it
is running.  The following comment in common/dom0_ops.c warns against this:

   /*
    * Can only create new VCPUs while the domain is not fully
    * constructed
    * (and hence not runnable). Xen needs auditing for races before
    * removing this check.
    */
    ret = -EINVAL;
    if ( test_bit(_VCPUF_initialised, &d->vcpu[0]->vcpu_flags) )
        goto maxvcpu_out;

Do you know which race condition is being avoided by this check for
_VCPUF_initialised?  Could it be the for_each_vcpu macro only checks for
null and a vcpu structure could be alloc''d but not initialized, and
then
used inside the macro?   

Thanks,
Ryan

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