From fa35e868f9ddcbb7984fd5ab7f91aef924fa8543 Mon Sep 17 00:00:00 2001
From: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Date: Mon, 10 Aug 2020 12:48:34 +0530
Subject: [PATCH] powerpc/smp: Implement cpu_to_coregroup_id
References: jsc#SLE-13617 bsc#1176912 ltc#186322
Patch-mainline: v5.10-rc1
Git-commit: fa35e868f9ddcbb7984fd5ab7f91aef924fa8543
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
Acked-by: Michal Suchanek <msuchanek@suse.de>
---
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 dfebca905acb..b725fb66e913 100644
--- a/arch/powerpc/mm/numa.c
+++ b/arch/powerpc/mm/numa.c
@@ -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);
}
--
2.28.0