Lookup the coregroup id from the associativity array. If unable to detect the coregroup id, fallback on the core id. This way, ensure sched_domain degenerates and an extra sched domain is not created.
Ideally this function should have been implemented in arch/powerpc/kernel/smp.c. However if its implemented in mm/numa.c, we don't need to find the primary domain again. If the device-tree mentions more than one coregroup, then kernel implements only the last or the smallest coregroup, which currently corresponds to the penultimate domain in the device-tree. Cc: linuxppc-dev <[email protected]> Cc: LKML <[email protected]> Cc: Michael Ellerman <[email protected]> Cc: Nicholas Piggin <[email protected]> Cc: Anton Blanchard <[email protected]> Cc: Oliver O'Halloran <[email protected]> Cc: Nathan Lynch <[email protected]> Cc: Michael Neuling <[email protected]> Cc: Gautham R Shenoy <[email protected]> Cc: Ingo Molnar <[email protected]> Cc: Peter Zijlstra <[email protected]> Cc: Valentin Schneider <[email protected]> Cc: Jordan Niethe <[email protected]> Reviewed-by : Gautham R. Shenoy <[email protected]> Signed-off-by: Srikar Dronamraju <[email protected]> --- Changelog v1 -> v2: Move coregroup_enabled before getting associativity (Gautham) arch/powerpc/mm/numa.c | 20 ++++++++++++++++++++ 1 file changed, 20 insertions(+) diff --git a/arch/powerpc/mm/numa.c b/arch/powerpc/mm/numa.c index ef8aa580da21..608e0fa61019 100644 --- a/arch/powerpc/mm/numa.c +++ b/arch/powerpc/mm/numa.c @@ -1218,6 +1218,26 @@ int find_and_online_cpu_nid(int cpu) int cpu_to_coregroup_id(int cpu) { + __be32 associativity[VPHN_ASSOC_BUFSIZE] = {0}; + int index; + + if (cpu < 0 || cpu > nr_cpu_ids) + return -1; + + if (!coregroup_enabled) + goto out; + + if (!firmware_has_feature(FW_FEATURE_VPHN)) + goto out; + + if (vphn_get_associativity(cpu, associativity)) + goto out; + + index = of_read_number(associativity, 1); + if (index > min_common_depth + 1) + return of_read_number(&associativity[index - 1], 1); + +out: return cpu_to_core_id(cpu); } -- 2.18.2
