+The type of siblings is (const) struct cpumask *.
+
+To be consistent on all architectures, include/linux/topology.h
+provides default definitions for any of the above macros that are
+not defined by include/asm-XXX/topology.h:
+1) physical_package_id: -1
+2) core_id: 0
+3) thread_siblings: just the given CPU
+4) core_siblings: just the given CPU
+
+Additionally, CPU topology information is provided under
+/sys/devices/system/cpu and includes these files. The internal
+source for the output is in brackets ("[]").
+
+ kernel_max: the maximum CPU index allowed by the kernel configuration.
+ [NR_CPUS-1]
+
+ offline: CPUs that are not online because they have been
+ HOTPLUGGED off (see cpu-hotplug.txt) or exceed the limit
+ of CPUs allowed by the kernel configuration (kernel_max
+ above). [~cpu_online_mask + cpus >= NR_CPUS]
+
+ online: CPUs that are online and being scheduled [cpu_online_mask]
+
+ possible: CPUs that have been allocated resources and can be
+ brought online if they are present. [cpu_possible_mask]
+
+ present: CPUs that have been identified as being present in the
+ system. [cpu_present_mask]
+
+The format for the above output is compatible with cpulist_parse()
+[see <linux/cpumask.h>]. Some examples follow.
+
+In this example, there are 64 CPUs in the system but cpus 32-63 exceed
+the kernel max which is limited to 0..31 by the NR_CPUS config option
+being 32. Note also that CPUs 2 and 4-31 are not online but could be
+brought online as they are both present and possible.