[PATCH v4 3/4] arm64: topology: Support SMT control on ACPI based system

[Yicong Yang]

From: Yicong Yang <yangyicong@xxxxxxxxxxxxx>

For ACPI we'll build the topology from PPTT and we cannot directly
get the SMT number of each core. Instead using a temporary xarray
to record the SMT number of each core when building the topology
and we can know the largest SMT number in the system. Then we can
notify the arch_topology for supporting SMT control.

Signed-off-by: Yicong Yang <yangyicong@xxxxxxxxxxxxx>
---
 arch/arm64/kernel/topology.c | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

diff --git a/arch/arm64/kernel/topology.c b/arch/arm64/kernel/topology.c
index 817d788cd866..0dc360c32ec8 100644
--- a/arch/arm64/kernel/topology.c
+++ b/arch/arm64/kernel/topology.c
@@ -17,6 +17,7 @@
 #include <linux/cpufreq.h>
 #include <linux/init.h>
 #include <linux/percpu.h>
+#include <linux/xarray.h>
 
 #include <asm/cpu.h>
 #include <asm/cputype.h>
@@ -43,11 +44,16 @@ static bool __init acpi_cpu_is_threaded(int cpu)
  */
 int __init parse_acpi_topology(void)
 {
+	int thread_num, max_smt_thread_num = 1;
+	struct xarray core_threads;
 	int cpu, topology_id;
+	void *entry;
 
 	if (acpi_disabled)
 		return 0;
 
+	xa_init(&core_threads);
+
 	for_each_possible_cpu(cpu) {
 		topology_id = find_acpi_cpu_topology(cpu, 0);
 		if (topology_id < 0)
@@ -57,6 +63,20 @@ int __init parse_acpi_topology(void)
 			cpu_topology[cpu].thread_id = topology_id;
 			topology_id = find_acpi_cpu_topology(cpu, 1);
 			cpu_topology[cpu].core_id   = topology_id;
+
+			entry = xa_load(&core_threads, topology_id);
+			if (!entry) {
+				xa_store(&core_threads, topology_id,
+					 xa_mk_value(1), GFP_KERNEL);
+			} else {
+				thread_num = xa_to_value(entry);
+				thread_num++;
+				xa_store(&core_threads, topology_id,
+					 xa_mk_value(thread_num), GFP_KERNEL);
+
+				if (thread_num > max_smt_thread_num)
+					max_smt_thread_num = thread_num;
+			}
 		} else {
 			cpu_topology[cpu].thread_id  = -1;
 			cpu_topology[cpu].core_id    = topology_id;
@@ -67,6 +87,9 @@ int __init parse_acpi_topology(void)
 		cpu_topology[cpu].package_id = topology_id;
 	}
 
+	topology_smt_set_num_threads(max_smt_thread_num);
+
+	xa_destroy(&core_threads);
 	return 0;
 }
 #endif
-- 
2.24.0