Commit fa35e868 authored Aug 10, 2020 by Srikar Dronamraju Committed by Michael Ellerman Sep 16, 2020

powerpc/smp: Implement cpu_to_coregroup_id



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.

Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Reviewed-by: Gautham R. Shenoy <ego@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200810071834.92514-11-srikar@linux.vnet.ibm.com

parent 72730bfc

arch/powerpc/mm/numa.c

+20 −0

Original line number	Diff line number	Diff line
		@@ -1247,6 +1247,26 @@ 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);
		}

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