diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig
index 83664db5221d..9b45f70549a7 100644
--- a/drivers/iommu/Kconfig
+++ b/drivers/iommu/Kconfig
@@ -3,6 +3,10 @@
 config IOMMU_IOVA
 	tristate
 
+# The IOASID library may also be used by non-IOMMU_API users
+config IOASID
+	tristate
+
 # IOMMU_API always gets selected by whoever wants it.
 config IOMMU_API
 	bool
diff --git a/drivers/iommu/Makefile b/drivers/iommu/Makefile
index 8c71a15e986b..0efac6f1ec73 100644
--- a/drivers/iommu/Makefile
+++ b/drivers/iommu/Makefile
@@ -7,6 +7,7 @@ obj-$(CONFIG_IOMMU_DMA) += dma-iommu.o
 obj-$(CONFIG_IOMMU_IO_PGTABLE) += io-pgtable.o
 obj-$(CONFIG_IOMMU_IO_PGTABLE_ARMV7S) += io-pgtable-arm-v7s.o
 obj-$(CONFIG_IOMMU_IO_PGTABLE_LPAE) += io-pgtable-arm.o
+obj-$(CONFIG_IOASID) += ioasid.o
 obj-$(CONFIG_IOMMU_IOVA) += iova.o
 obj-$(CONFIG_OF_IOMMU)	+= of_iommu.o
 obj-$(CONFIG_MSM_IOMMU) += msm_iommu.o
diff --git a/drivers/iommu/ioasid.c b/drivers/iommu/ioasid.c
new file mode 100644
index 000000000000..bbb771214fa9
--- /dev/null
+++ b/drivers/iommu/ioasid.c
@@ -0,0 +1,150 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * I/O Address Space ID allocator. There is one global IOASID space, split into
+ * subsets. Users create a subset with DECLARE_IOASID_SET, then allocate and
+ * free IOASIDs with ioasid_alloc and ioasid_free.
+ */
+#include <linux/ioasid.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/spinlock.h>
+#include <linux/xarray.h>
+
+struct ioasid_data {
+	ioasid_t id;
+	struct ioasid_set *set;
+	void *private;
+	struct rcu_head rcu;
+};
+
+static DEFINE_XARRAY_ALLOC(ioasid_xa);
+
+/**
+ * ioasid_set_data - Set private data for an allocated ioasid
+ * @ioasid: the ID to set data
+ * @data:   the private data
+ *
+ * For IOASID that is already allocated, private data can be set
+ * via this API. Future lookup can be done via ioasid_find.
+ */
+int ioasid_set_data(ioasid_t ioasid, void *data)
+{
+	struct ioasid_data *ioasid_data;
+	int ret = 0;
+
+	xa_lock(&ioasid_xa);
+	ioasid_data = xa_load(&ioasid_xa, ioasid);
+	if (ioasid_data)
+		rcu_assign_pointer(ioasid_data->private, data);
+	else
+		ret = -ENOENT;
+	xa_unlock(&ioasid_xa);
+
+	/*
+	 * Wait for readers to stop accessing the old private data, so the
+	 * caller can free it.
+	 */
+	if (!ret)
+		synchronize_rcu();
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(ioasid_set_data);
+
+/**
+ * ioasid_alloc - Allocate an IOASID
+ * @set: the IOASID set
+ * @min: the minimum ID (inclusive)
+ * @max: the maximum ID (inclusive)
+ * @private: data private to the caller
+ *
+ * Allocate an ID between @min and @max. The @private pointer is stored
+ * internally and can be retrieved with ioasid_find().
+ *
+ * Return: the allocated ID on success, or %INVALID_IOASID on failure.
+ */
+ioasid_t ioasid_alloc(struct ioasid_set *set, ioasid_t min, ioasid_t max,
+		      void *private)
+{
+	u32 id = INVALID_IOASID;
+	struct ioasid_data *data;
+
+	data = kzalloc(sizeof(*data), GFP_KERNEL);
+	if (!data)
+		return INVALID_IOASID;
+
+	data->set = set;
+	data->private = private;
+
+	if (xa_alloc(&ioasid_xa, &id, data, XA_LIMIT(min, max), GFP_KERNEL)) {
+		pr_err("Failed to alloc ioasid from %d to %d\n", min, max);
+		goto exit_free;
+	}
+	data->id = id;
+
+exit_free:
+	if (id == INVALID_IOASID) {
+		kfree(data);
+		return INVALID_IOASID;
+	}
+	return id;
+}
+EXPORT_SYMBOL_GPL(ioasid_alloc);
+
+/**
+ * ioasid_free - Free an IOASID
+ * @ioasid: the ID to remove
+ */
+void ioasid_free(ioasid_t ioasid)
+{
+	struct ioasid_data *ioasid_data;
+
+	ioasid_data = xa_erase(&ioasid_xa, ioasid);
+
+	kfree_rcu(ioasid_data, rcu);
+}
+EXPORT_SYMBOL_GPL(ioasid_free);
+
+/**
+ * ioasid_find - Find IOASID data
+ * @set: the IOASID set
+ * @ioasid: the IOASID to find
+ * @getter: function to call on the found object
+ *
+ * The optional getter function allows to take a reference to the found object
+ * under the rcu lock. The function can also check if the object is still valid:
+ * if @getter returns false, then the object is invalid and NULL is returned.
+ *
+ * If the IOASID has been allocated for this set, return the private pointer
+ * passed to ioasid_alloc. Private data can be NULL if not set. Return an error
+ * if the IOASID is not found or does not belong to the set.
+ */
+void *ioasid_find(struct ioasid_set *set, ioasid_t ioasid,
+		  bool (*getter)(void *))
+{
+	void *priv = NULL;
+	struct ioasid_data *ioasid_data;
+
+	rcu_read_lock();
+	ioasid_data = xa_load(&ioasid_xa, ioasid);
+	if (!ioasid_data) {
+		priv = ERR_PTR(-ENOENT);
+		goto unlock;
+	}
+	if (set && ioasid_data->set != set) {
+		/* data found but does not belong to the set */
+		priv = ERR_PTR(-EACCES);
+		goto unlock;
+	}
+	/* Now IOASID and its set is verified, we can return the private data */
+	priv = rcu_dereference(ioasid_data->private);
+	if (getter && !getter(priv))
+		priv = NULL;
+unlock:
+	rcu_read_unlock();
+
+	return priv;
+}
+EXPORT_SYMBOL_GPL(ioasid_find);
+
+MODULE_LICENSE("GPL");
diff --git a/include/linux/ioasid.h b/include/linux/ioasid.h
new file mode 100644
index 000000000000..940212422b8f
--- /dev/null
+++ b/include/linux/ioasid.h
@@ -0,0 +1,49 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __LINUX_IOASID_H
+#define __LINUX_IOASID_H
+
+#include <linux/types.h>
+
+#define INVALID_IOASID ((ioasid_t)-1)
+typedef unsigned int ioasid_t;
+
+struct ioasid_set {
+	int dummy;
+};
+
+#define DECLARE_IOASID_SET(name) struct ioasid_set name = { 0 }
+
+#if IS_ENABLED(CONFIG_IOASID)
+ioasid_t ioasid_alloc(struct ioasid_set *set, ioasid_t min, ioasid_t max,
+		      void *private);
+void ioasid_free(ioasid_t ioasid);
+
+void *ioasid_find(struct ioasid_set *set, ioasid_t ioasid,
+		  bool (*getter)(void *));
+
+int ioasid_set_data(ioasid_t ioasid, void *data);
+
+#else /* !CONFIG_IOASID */
+static inline ioasid_t ioasid_alloc(struct ioasid_set *set, ioasid_t min,
+				    ioasid_t max, void *private)
+{
+	return INVALID_IOASID;
+}
+
+static inline void ioasid_free(ioasid_t ioasid)
+{
+}
+
+static inline void *ioasid_find(struct ioasid_set *set, ioasid_t ioasid,
+				bool (*getter)(void *))
+{
+	return NULL;
+}
+
+static inline int ioasid_set_data(ioasid_t ioasid, void *data)
+{
+	return -ENODEV;
+}
+
+#endif /* CONFIG_IOASID */
+#endif /* __LINUX_IOASID_H */
