On summit-based machines the cpu_sibling_map data has been hosed for some
time. I found out why in Intel's IA-32 Software Deveveopers' Manual Vol 2
under CPUID. Looks like the value that cpuid returns is the one latched at
reset, and doesn't reflect any changes made by the BIOS later:
* Local APIC ID (high byte of EBX)--this number is the 8-bit ID that
is assigned to the local APIC on the processor during power up. This
field was introduced in the Pentium 4 processor.
Also, the code in init_intel was a bit overdesigned. Until Intel releases
a chip with a non-power-of-2 sibling count on it, there's no point in all
that bit bashing.