[tip: perf/core] perf/x86/intel/uncore: Fix uncore_die_to_cpu() for offline dies

[tip-bot2 for Zide Chen]

The following commit has been merged into the perf/core branch of tip:

Commit-ID:     2aa7dacf8a3d928303df9c770c1bd7f50d1f8f2a
Gitweb:        https://git.kernel.org/tip/2aa7dacf8a3d928303df9c770c1bd7f50d1f8f2a
Author:        Zide Chen <zide.chen@xxxxxxxxx>
AuthorDate:    Tue, 02 Jun 2026 07:49:07 -07:00
Committer:     Peter Zijlstra <peterz@xxxxxxxxxxxxx>
CommitterDate: Thu, 04 Jun 2026 11:38:37 +02:00

perf/x86/intel/uncore: Fix uncore_die_to_cpu() for offline dies

If the die is offline when uncore_die_to_cpu() is called, it silently
returns 0, which is misleading.  Return -1 in this case to indicate
that all CPUs on the die are offline and the caller can take care of
it accordingly.

Opportunistically, replace -EPERM with -ENODEV, as -ENODEV is
the appropriate error when no CPUs are online across all dies.

Signed-off-by: Zide Chen <zide.chen@xxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Reviewed-by: Dapeng Mi <dapeng1.mi@xxxxxxxxxxxxxxx>
Link: https://patch.msgid.link/20260602144908.263680-7-zide.chen@xxxxxxxxx
---
 arch/x86/events/intel/uncore.c       |  2 +-
 arch/x86/events/intel/uncore_snbep.c |  9 +++++++--
 2 files changed, 8 insertions(+), 3 deletions(-)

diff --git a/arch/x86/events/intel/uncore.c b/arch/x86/events/intel/uncore.c
index 22256de..4b3a1fa 100644
--- a/arch/x86/events/intel/uncore.c
+++ b/arch/x86/events/intel/uncore.c
@@ -91,7 +91,7 @@ int uncore_device_to_die(struct pci_dev *dev)
  */
 int uncore_die_to_cpu(int die)
 {
-	int res = 0, cpu;
+	int res = -1, cpu;
 
 	for_each_online_cpu(cpu) {
 		if (topology_logical_die_id(cpu) == die) {
diff --git a/arch/x86/events/intel/uncore_snbep.c b/arch/x86/events/intel/uncore_snbep.c
index 772b782..334dc38 100644
--- a/arch/x86/events/intel/uncore_snbep.c
+++ b/arch/x86/events/intel/uncore_snbep.c
@@ -3772,12 +3772,17 @@ static void pmu_free_topology(struct intel_uncore_type *type)
 static int skx_pmu_get_topology(struct intel_uncore_type *type,
 				 int (*topology_cb)(struct intel_uncore_type*, int, int, u64))
 {
-	int die, ret = -EPERM;
+	int die, ret = -ENODEV;
 	u64 cpu_bus_msr;
+	int cpu;
 
 	cpus_read_lock();
 	for (die = 0; die < uncore_max_dies(); die++) {
-		ret = skx_msr_cpu_bus_read(uncore_die_to_cpu(die), &cpu_bus_msr);
+		cpu = uncore_die_to_cpu(die);
+		if (cpu == -1)
+			continue;
+
+		ret = skx_msr_cpu_bus_read(cpu, &cpu_bus_msr);
 		if (ret)
 			break;