iommu: Fix race between OF and IOMMU device probe codepaths

Something something not sure if this is fully correct.

Signed-off-by: Hector Martin <[email protected]>

Author: marcan

drivers/iommu/iommu.c

@@ -333,12 +333,13 @@ static u32 dev_iommu_get_max_pasids(struct device *dev)
 	return min_t(u32, max_pasids, dev->iommu->iommu_dev->max_pasids);
 }
 
+DEFINE_MUTEX(iommu_probe_device_lock);
+
 static int __iommu_probe_device(struct device *dev, struct list_head *group_list)
 {
 	const struct iommu_ops *ops = dev->bus->iommu_ops;
 	struct iommu_device *iommu_dev;
 	struct iommu_group *group;
-	static DEFINE_MUTEX(iommu_probe_device_lock);
 	int ret;
 
 	if (!ops)

drivers/iommu/of_iommu.c

@@ -107,20 +107,30 @@ static int of_iommu_configure_device(struct device_node *master_np,
 		      of_iommu_configure_dev(master_np, dev);
 }
 
+extern struct mutex iommu_probe_device_lock;
+
 const struct iommu_ops *of_iommu_configure(struct device *dev,
 					   struct device_node *master_np,
 					   const u32 *id)
 {
 	const struct iommu_ops *ops = NULL;
-	struct iommu_fwspec *fwspec = dev_iommu_fwspec_get(dev);
+	struct iommu_fwspec *fwspec;
 	int err = NO_IOMMU;
 
-	if (!master_np)
+	mutex_lock(&iommu_probe_device_lock);
+
+	if (!master_np) {
+		mutex_unlock(&iommu_probe_device_lock);
 		return NULL;
+	}
+
+	fwspec = dev_iommu_fwspec_get(dev);
 
 	if (fwspec) {
-		if (fwspec->ops)
+		if (fwspec->ops) {
+			mutex_unlock(&iommu_probe_device_lock);
 			return fwspec->ops;
+		}
 
 		/* In the deferred case, start again from scratch */
 		iommu_fwspec_free(dev);
@@ -155,6 +165,9 @@ const struct iommu_ops *of_iommu_configure(struct device *dev,
 		fwspec = dev_iommu_fwspec_get(dev);
 		ops    = fwspec->ops;
 	}
+
+	mutex_unlock(&iommu_probe_device_lock);
+
 	/*
 	 * If we have reason to believe the IOMMU driver missed the initial
 	 * probe for dev, replay it to get things in order.