[PATCH v2 1/2] arch_topology: Reset SMT state when socket parsing fails

[PATCH v2 1/2] arch_topology: Reset SMT state when socket parsing fails

[Sudeep Holla]

If a later socket's cluster fails device tree parsing, parse_socket()
returns immediately. Cores parsed earlier can have raised
max_smt_thread_num, but this return skips the reset to 1 and the
cpu_smt_set_num_threads() notification. The framework is left with an
inconsistent SMT state after topology parsing fails.

Break out of the socket loop on parse_cluster() failure so the existing
error handling resets the thread count and notifies the SMT framework
before returning the error.

Reported-by: Sashiko <sashiko-bot@kernel.org>
Closes: https://sashiko.dev/#/bug/linux-73adead8-21f3-470d-938c-b1f07a269a72
Fixes: 5deb9c789ae4 ("arch_topology: Support SMT control for OF based system")
Signed-off-by: Sudeep Holla <sudeep.holla@kernel.org>
---
 drivers/base/arch_topology.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

v1->v2:
 - No change(just posting together with 2/2 which was result of sashiko review)
 - v1: https://lore.kernel.org/all/20261103093421.1283949-1-sudeep.holla@kernel.org

diff --git a/drivers/base/arch_topology.c b/drivers/base/arch_topology.c
index 8c5e47c28d9a..1569ab3335f5 100644
--- a/drivers/base/arch_topology.c
+++ b/drivers/base/arch_topology.c
@@ -633,7 +633,7 @@ static int __init parse_socket(struct device_node *socket)
 		has_socket = true;
 		ret = parse_cluster(c, package_id, -1, 0);
 		if (ret != 0)
-			return ret;
+			break;
 
 		package_id++;
 	} while (1);
-- 
2.43.0

[PATCH v2 2/2] arch_topology: Free ACPI SMT entries on lookup failure

[Sudeep Holla]

A later CPU can fail find_acpi_cpu_topology() after earlier threaded
CPUs have populated hetero_cpu. Returning immediately leaks the stored
cpu_smt_info objects and the XArray nodes.

Send the error through the existing cleanup and retain its return code.
Only update the SMT thread count after a successful parse.

Reported-by: Sashiko <sashiko-bot@kernel.org>
Closes: https://sashiko.dev/#/bug/linux-f41acdf3-9470-4de9-b497-d5de16c8e7e8
Fixes: e6b18ebfaf63 ("arm64: topology: Support SMT control on ACPI based system")
Signed-off-by: Sudeep Holla <sudeep.holla@kernel.org>
---
 drivers/base/arch_topology.c | 15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

v1->v2:
 - Reset max_smt_thread_num to 1 on failure similar to parse_socket()
 - v1: https://lore.kernel.org/all/20261104153413.2786066-1-sudeep.holla@kernel.org

diff --git a/drivers/base/arch_topology.c b/drivers/base/arch_topology.c
index 1569ab3335f5..9033a9b642e3 100644
--- a/drivers/base/arch_topology.c
+++ b/drivers/base/arch_topology.c
@@ -860,7 +860,7 @@ __weak int __init parse_acpi_topology(void)
 	struct cpu_smt_info *entry;
 	struct xarray hetero_cpu;
 	unsigned long hetero_id;
-	int cpu, topology_id;
+	int cpu, topology_id, ret = 0;
 
 	if (acpi_disabled)
 		return 0;
@@ -869,8 +869,10 @@ __weak int __init parse_acpi_topology(void)
 
 	for_each_possible_cpu(cpu) {
 		topology_id = find_acpi_cpu_topology(cpu, 0);
-		if (topology_id < 0)
-			return topology_id;
+		if (topology_id < 0) {
+			ret = topology_id;
+			goto out;
+		}
 
 		if (acpi_cpu_is_threaded(cpu)) {
 			cpu_topology[cpu].thread_id = topology_id;
@@ -914,6 +916,7 @@ __weak int __init parse_acpi_topology(void)
 		cpu_topology[cpu].package_id = topology_id;
 	}
 
+out:
 	/*
 	 * This is a short loop since the number of XArray elements is the
 	 * number of heterogeneous CPU clusters. On a homogeneous system
@@ -925,9 +928,13 @@ __weak int __init parse_acpi_topology(void)
 		kfree(entry);
 	}
 
+	/* Reset max_smt_thread_num to 1 on failure like in parse_socket() */
+	if (ret)
+		max_smt_thread_num = 1;
+
 	cpu_smt_set_num_threads(max_smt_thread_num, max_smt_thread_num);
 	xa_destroy(&hetero_cpu);
-	return 0;
+	return ret;
 }
 
 void __init init_cpu_topology(void)
-- 
2.43.0