[PATCH] arch_topology: Swap MC & CLS SD mask if MC weight==1 & subset(MC,CLS)

[Dietmar Eggemann]

This avoids the issue of having a system with a CLS SD but no MC SD.
CLS should be sub-SD of MC.

The cpumask under /sys/devices/system/cpu/cpu*/cache/index* and
/sys/devices/system/cpu/cpu*/topology are not changed by this.

Signed-off-by: Dietmar Eggemann <dietmar.eggemann@xxxxxxx>
---
 drivers/base/arch_topology.c | 30 ++++++++++++++++++++++++++++--
 1 file changed, 28 insertions(+), 2 deletions(-)

diff --git a/drivers/base/arch_topology.c b/drivers/base/arch_topology.c
index 976154140f0b..9af90a5625c7 100644
--- a/drivers/base/arch_topology.c
+++ b/drivers/base/arch_topology.c
@@ -614,7 +614,7 @@ static int __init parse_dt_topology(void)
 struct cpu_topology cpu_topology[NR_CPUS];
 EXPORT_SYMBOL_GPL(cpu_topology);
 
-const struct cpumask *cpu_coregroup_mask(int cpu)
+const struct cpumask *_cpu_coregroup_mask(int cpu)
 {
 	const cpumask_t *core_mask = cpumask_of_node(cpu_to_node(cpu));
 
@@ -631,11 +631,37 @@ const struct cpumask *cpu_coregroup_mask(int cpu)
 	return core_mask;
 }
 
-const struct cpumask *cpu_clustergroup_mask(int cpu)
+const struct cpumask *_cpu_clustergroup_mask(int cpu)
 {
 	return &cpu_topology[cpu].cluster_sibling;
 }
 
+static int
+swap_masks(const cpumask_t *core_mask, const cpumask_t *cluster_mask)
+{
+	if (cpumask_weight(core_mask) == 1 &&
+	    cpumask_subset(core_mask, cluster_mask))
+		return 1;
+
+	return 0;
+}	
+
+const struct cpumask *cpu_coregroup_mask(int cpu)
+{
+	const cpumask_t *cluster_mask = _cpu_clustergroup_mask(cpu);
+	const cpumask_t *core_mask = _cpu_coregroup_mask(cpu);
+	
+	return swap_masks(core_mask, cluster_mask) ? cluster_mask : core_mask;
+}
+
+const struct cpumask *cpu_clustergroup_mask(int cpu)
+{
+	const cpumask_t *cluster_mask = _cpu_clustergroup_mask(cpu);
+	const cpumask_t *core_mask = _cpu_coregroup_mask(cpu);
+
+	return swap_masks(core_mask, cluster_mask) ? core_mask : cluster_mask;
+}
+
 void update_siblings_masks(unsigned int cpuid)
 {
 	struct cpu_topology *cpu_topo, *cpuid_topo = &cpu_topology[cpuid];
-- 
2.25.1