Comment 19 for bug 1304001

I also would rather like to find a proper fix than just revert that commit. Andrew, can you provide the info Boris was asking for? And just in general, is there something else that looks or goes wrong in the guest. The error looks to be originating from add_memory and EEXIST may be returned if register_memory_resource fails (though should do a pr_debug) or if it is not a new node (with another additional printk). So it sounds likely it it is the former (register_memory_resource) and adding a
  dyndbg="file xen-balloon.c +p"
to the guests grub command line would activate the additional pr_debug lines.