From bfcc4397435dc0407099b9a805391abc05c2313b Mon Sep 17 00:00:00 2001 From: Ionela Voinescu Date: Mon, 4 Jul 2022 11:16:01 +0100 Subject: [PATCH] arch_topology: Limit span of cpu_clustergroup_mask() Currently the cluster identifier is not set on DT based platforms. The reset or default value is -1 for all the CPUs. Once we assign the cluster identifier values correctly, the cluster_sibling mask will be populated and returned by cpu_clustergroup_mask() to contribute in the creation of the CLS scheduling domain level, if SCHED_CLUSTER is enabled. To avoid topologies that will result in questionable or incorrect scheduling domains, impose restrictions regarding the span of clusters, as presented to scheduling domains building code: cluster_sibling should not span more or the same CPUs as cpu_coregroup_mask(). This is needed in order to obtain a strict separation between the MC and CLS levels, and maintain the same domains for existing platforms in the presence of CONFIG_SCHED_CLUSTER, where the new cluster information is redundant and irrelevant for the scheduler. While previously the scheduling domain builder code would have removed MC as redundant and kept CLS if SCHED_CLUSTER was enabled and the cpu_coregroup_mask() and cpu_clustergroup_mask() spanned the same CPUs, now CLS will be removed and MC kept. Link: https://lore.kernel.org/r/20220704101605.1318280-18-sudeep.holla@arm.com Cc: Darren Hart Tested-by: Conor Dooley Acked-by: Vincent Guittot Signed-off-by: Ionela Voinescu Signed-off-by: Sudeep Holla --- drivers/base/arch_topology.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/drivers/base/arch_topology.c b/drivers/base/arch_topology.c index e384afb6cac7..591c1f8e15e2 100644 --- a/drivers/base/arch_topology.c +++ b/drivers/base/arch_topology.c @@ -686,6 +686,14 @@ const struct cpumask *cpu_coregroup_mask(int cpu) const struct cpumask *cpu_clustergroup_mask(int cpu) { + /* + * Forbid cpu_clustergroup_mask() to span more or the same CPUs as + * cpu_coregroup_mask(). + */ + if (cpumask_subset(cpu_coregroup_mask(cpu), + &cpu_topology[cpu].cluster_sibling)) + return get_cpu_mask(cpu); + return &cpu_topology[cpu].cluster_sibling; }