On 08/03/18 17:44, Jonathan Cameron wrote:

quoted

@@ -3168,6 +3260,13 @@ static int arm_smmu_device_probe(struct platform_device *pdev)
 	if (ret)
 		return ret;
 
+	if (smmu->features & (ARM_SMMU_FEAT_STALLS | ARM_SMMU_FEAT_PRI)) {
+		smmu->faultq_nb.notifier_call = arm_smmu_flush_queues;
+		ret = iommu_fault_queue_register(&smmu->faultq_nb);

Here you register only if this smmu supports stalls or pri which is fine, but
see the unregister path.

quoted

+		if (ret)
+			return ret;
+	}
+
 	/* And we're up. Go go go! */
 	ret = iommu_device_sysfs_add(&smmu->iommu, dev, NULL,
 				     "smmu3.%pa", &ioaddr);

@@ -3210,6 +3309,8 @@ static int arm_smmu_device_remove(struct platform_device *pdev)
 {
 	struct arm_smmu_device *smmu = platform_get_drvdata(pdev);
 
+	iommu_fault_queue_unregister(&smmu->faultq_nb);

Here you unregister from the fault queue unconditionally.  That is mostly
safe but it seems to decrement and potentially destroy the work queue that
is in use by another smmu instance that does support page faulting.

Ah yes, we'll need to check this

Thanks,
Jean