linux-kernel - [PATCH V2 1/2] perf/x86/intel/uncore: Skip discovery table for offline dies

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Message-ID: <20260113205650.5201-1-zide.chen@intel.com>
Date: Tue, 13 Jan 2026 12:56:49 -0800
From: Zide Chen <zide.chen@...el.com>
To: Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...hat.com>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Namhyung Kim <namhyung@...nel.org>,
	Ian Rogers <irogers@...gle.com>,
	Adrian Hunter <adrian.hunter@...el.com>,
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
	Andi Kleen <ak@...ux.intel.com>,
	Eranian Stephane <eranian@...gle.com>
Cc: linux-kernel@...r.kernel.org,
	linux-perf-users@...r.kernel.org,
	Dapeng Mi <dapeng1.mi@...ux.intel.com>,
	Zide Chen <zide.chen@...el.com>,
	Xudong Hao <xudong.hao@...el.com>,
	Falcon Thomas <thomas.falcon@...el.com>,
	Steve Wahl <steve.wahl@....com>
Subject: [PATCH V2 1/2] perf/x86/intel/uncore: Skip discovery table for offline dies

This warning can be triggered if NUMA is disabled and the system
boots with fewer CPUs than the number of CPUs in die 0.

WARNING: CPU: 9 PID: 7257 at uncore.c:1157 uncore_pci_pmu_register+0x136/0x160 [intel_uncore]

Currently, the discovery table continues to be parsed even if all CPUs
in the associated die are offline.  This can lead to an array overflow
at "pmu->boxes[die] = box" in uncore_pci_pmu_register(), which may
trigger the warning above or cause other issues.

Reported-by: Steve Wahl <steve.wahl@....com>
Tested-by: Steve Wahl <steve.wahl@....com>
Fixes: edae1f06c2cd ("perf/x86/intel/uncore: Parse uncore discovery tables")
Signed-off-by: Zide Chen <zide.chen@...el.com>
---
V2:
- Add the Tested-by tag
- Rebase onto perf/core (base commit: a491c02c2770)

 arch/x86/events/intel/uncore.c           | 4 ++++
 arch/x86/events/intel/uncore_discovery.c | 2 +-
 2 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/arch/x86/events/intel/uncore.c b/arch/x86/events/intel/uncore.c
index 4684649109d9..c126a29ab729 100644
--- a/arch/x86/events/intel/uncore.c
+++ b/arch/x86/events/intel/uncore.c
@@ -1368,6 +1368,10 @@ static void uncore_pci_pmus_register(void)
 
 		for (node = rb_first(type->boxes); node; node = rb_next(node)) {
 			unit = rb_entry(node, struct intel_uncore_discovery_unit, node);
+
+			if (WARN_ON(unit->die >= uncore_max_dies()))
+				continue;
+
 			pdev = pci_get_domain_bus_and_slot(UNCORE_DISCOVERY_PCI_DOMAIN(unit->addr),
 							   UNCORE_DISCOVERY_PCI_BUS(unit->addr),
 							   UNCORE_DISCOVERY_PCI_DEVFN(unit->addr));
diff --git a/arch/x86/events/intel/uncore_discovery.c b/arch/x86/events/intel/uncore_discovery.c
index b46575254dbe..0e414cecb6f2 100644
--- a/arch/x86/events/intel/uncore_discovery.c
+++ b/arch/x86/events/intel/uncore_discovery.c
@@ -366,7 +366,7 @@ static bool uncore_discovery_pci(struct uncore_discovery_domain *domain)
 				     (val & UNCORE_DISCOVERY_DVSEC2_BIR_MASK) * UNCORE_DISCOVERY_BIR_STEP;
 
 			die = get_device_die_id(dev);
-			if (die < 0)
+			if ((die < 0) || (die >= uncore_max_dies()))
 				continue;
 
 			parse_discovery_table(domain, dev, die, bar_offset, &parsed);
-- 
2.52.0