Venkatesh Pallipadi
authored
Clustered APIC setup patch. Needed to support generic systems with more
than 8 CPUs.
Motivation:
The current APIC destination mode ("Flat Logical") used in linux kernel
has an upper limit of 8 CPUs. For more than 8 CPUs, either "Clustered
Logical" or "Physical" mode has to be used.
The attached patch adds support such systems by organizing them into
logical clusters, with each cluster having 4 CPUs. This is activated by
a new config option "Support for other sub-arch SMP systems with more
than 8 CPUs", under Processor feature->Sub architecture.
The patch is made very simple and isolated, thanks to Martin J.
Bligh's patchsets, which has moved all APIC related functions into
sub-arch macros. Has zero impact on standard systems.
This patch enables all 16 logical processors on a generic, non-quad
based, system that we have here. Also, by looking at SuSE source, I
have also added a special switch, to specifically support Unisys
(ES7000). Just replacing #define SEQUENTIAL_APICID by CLUSTERED_APICID
in the patch should make it work on ES7000(not tested).