perf/x86/intel/uncore: Register the PMU only if the uncore pci device exists

Current code registers PMUs for all possible uncore pci devices.
This is not good because, on some machines, one or more uncore pci
devices can be missing. The missing pci device make corresponding
PMU unusable. Register the PMU only if the uncore device exists.

Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>
Signed-off-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: eranian@google.com
Link: http://lkml.kernel.org/r/1409872109-31645-3-git-send-email-andi@firstfloor.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

arch/x86/kernel/cpu/perf_event_intel_uncore.c

@@ -793,6 +793,7 @@ static int uncore_pci_probe(struct pci_dev *pdev, const struct pci_device_id *id
 	struct intel_uncore_box *box;
 	struct intel_uncore_type *type;
 	int phys_id;
+	bool first_box = false;
 
 	phys_id = uncore_pcibus_to_physid[pdev->bus->number];
 	if (phys_id < 0)
@@ -827,9 +828,13 @@ static int uncore_pci_probe(struct pci_dev *pdev, const struct pci_device_id *id
 	pci_set_drvdata(pdev, box);
 
 	raw_spin_lock(&uncore_box_lock);
+	if (list_empty(&pmu->box_list))
+		first_box = true;
 	list_add_tail(&box->list, &pmu->box_list);
 	raw_spin_unlock(&uncore_box_lock);
 
+	if (first_box)
+		uncore_pmu_register(pmu);
 	return 0;
 }
 
@@ -838,6 +843,7 @@ static void uncore_pci_remove(struct pci_dev *pdev)
 	struct intel_uncore_box *box = pci_get_drvdata(pdev);
 	struct intel_uncore_pmu *pmu;
 	int i, cpu, phys_id = uncore_pcibus_to_physid[pdev->bus->number];
+	bool last_box = false;
 
 	box = pci_get_drvdata(pdev);
 	if (!box) {
@@ -859,6 +865,8 @@ static void uncore_pci_remove(struct pci_dev *pdev)
 
 	raw_spin_lock(&uncore_box_lock);
 	list_del(&box->list);
+	if (list_empty(&pmu->box_list))
+		last_box = true;
 	raw_spin_unlock(&uncore_box_lock);
 
 	for_each_possible_cpu(cpu) {
@@ -870,6 +878,9 @@ static void uncore_pci_remove(struct pci_dev *pdev)
 
 	WARN_ON_ONCE(atomic_read(&box->refcnt) != 1);
 	kfree(box);
+
+	if (last_box)
+		perf_pmu_unregister(&pmu->pmu);
 }
 
 static int __init uncore_pci_init(void)
@@ -1221,14 +1232,6 @@ static int __init uncore_pmus_register(void)
 		}
 	}
 
-	for (i = 0; uncore_pci_uncores[i]; i++) {
-		type = uncore_pci_uncores[i];
-		for (j = 0; j < type->num_boxes; j++) {
-			pmu = &type->pmus[j];
-			uncore_pmu_register(pmu);
-		}
-	}
-
 	return 0;
 }