From 63f48abd55d0417996bca86022925c853a2b436b Mon Sep 17 00:00:00 2001 From: Zide Chen Date: Tue, 2 Jun 2026 07:49:02 -0700 Subject: [PATCH] perf/x86/intel/uncore: Fix discovery unit lookup for multi-die systems In uncore_find_add_unit(), PMON units with the same unit ID may be added to the uncore discovery RB-tree for different dies. These units are distinguished by node->die. However, intel_generic_uncore_box_ctl() uses a fixed die ID of -1 when looking up the discovery unit, which may retrieve the wrong node on multi-die systems. Use box->dieid instead so the correct discovery unit is selected. No functional issue has been observed so far because currently supported platforms happen to use the same unit control register for such units. Remove WARN_ON_ONCE() because with the above change a NULL unit can be expected, e.g. when a CPU die is offline during uncore enumeration and the unit is not added to the RB-tree. In this case, intel_uncore_find_discovery_unit() returns NULL once the die becomes online, and it is expected that the PMU box is not functional for that die. Fixes: b1d9ea2e1ca4 ("perf/x86/uncore: Apply the unit control RB tree to MSR uncore units") Signed-off-by: Zide Chen Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Dapeng Mi Link: https://patch.msgid.link/20260602144908.263680-2-zide.chen@intel.com --- arch/x86/events/intel/uncore_discovery.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/arch/x86/events/intel/uncore_discovery.c b/arch/x86/events/intel/uncore_discovery.c index 583cbd06b9b8..60e1200c4691 100644 --- a/arch/x86/events/intel/uncore_discovery.c +++ b/arch/x86/events/intel/uncore_discovery.c @@ -481,8 +481,8 @@ static u64 intel_generic_uncore_box_ctl(struct intel_uncore_box *box) struct intel_uncore_discovery_unit *unit; unit = intel_uncore_find_discovery_unit(box->pmu->type->boxes, - -1, box->pmu->pmu_idx); - if (WARN_ON_ONCE(!unit)) + box->dieid, box->pmu->pmu_idx); + if (!unit) return 0; return unit->addr;