1 files changed, 422 insertions, 0 deletions
diff --git a/drivers/iommu/ioasid.c b/drivers/iommu/ioasid.c
new file mode 100644
index 000000000000..0f8dd377aada
--- /dev/null
+++ b/drivers/iommu/ioasid.c
@@ -0,0 +1,422 @@
+// 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;
+};
+
+/*
+ * struct ioasid_allocator_data - Internal data structure to hold information
+ * about an allocator. There are two types of allocators:
+ *
+ * - Default allocator always has its own XArray to track the IOASIDs allocated.
+ * - Custom allocators may share allocation helpers with different private data.
+ *   Custom allocators that share the same helper functions also share the same
+ *   XArray.
+ * Rules:
+ * 1. Default allocator is always available, not dynamically registered. This is
+ *    to prevent race conditions with early boot code that want to register
+ *    custom allocators or allocate IOASIDs.
+ * 2. Custom allocators take precedence over the default allocator.
+ * 3. When all custom allocators sharing the same helper functions are
+ *    unregistered (e.g. due to hotplug), all outstanding IOASIDs must be
+ *    freed. Otherwise, outstanding IOASIDs will be lost and orphaned.
+ * 4. When switching between custom allocators sharing the same helper
+ *    functions, outstanding IOASIDs are preserved.
+ * 5. When switching between custom allocator and default allocator, all IOASIDs
+ *    must be freed to ensure unadulterated space for the new allocator.
+ *
+ * @ops:	allocator helper functions and its data
+ * @list:	registered custom allocators
+ * @slist:	allocators share the same ops but different data
+ * @flags:	attributes of the allocator
+ * @xa:		xarray holds the IOASID space
+ * @rcu:	used for kfree_rcu when unregistering allocator
+ */
+struct ioasid_allocator_data {
+	struct ioasid_allocator_ops *ops;
+	struct list_head list;
+	struct list_head slist;
+#define IOASID_ALLOCATOR_CUSTOM BIT(0) /* Needs framework to track results */
+	unsigned long flags;
+	struct xarray xa;
+	struct rcu_head rcu;
+};
+
+static DEFINE_SPINLOCK(ioasid_allocator_lock);
+static LIST_HEAD(allocators_list);
+
+static ioasid_t default_alloc(ioasid_t min, ioasid_t max, void *opaque);
+static void default_free(ioasid_t ioasid, void *opaque);
+
+static struct ioasid_allocator_ops default_ops = {
+	.alloc = default_alloc,
+	.free = default_free,
+};
+
+static struct ioasid_allocator_data default_allocator = {
+	.ops = &default_ops,
+	.flags = 0,
+	.xa = XARRAY_INIT(ioasid_xa, XA_FLAGS_ALLOC),
+};
+
+static struct ioasid_allocator_data *active_allocator = &default_allocator;
+
+static ioasid_t default_alloc(ioasid_t min, ioasid_t max, void *opaque)
+{
+	ioasid_t id;
+
+	if (xa_alloc(&default_allocator.xa, &id, opaque, XA_LIMIT(min, max), GFP_ATOMIC)) {
+		pr_err("Failed to alloc ioasid from %d to %d\n", min, max);
+		return INVALID_IOASID;
+	}
+
+	return id;
+}
+
+static void default_free(ioasid_t ioasid, void *opaque)
+{
+	struct ioasid_data *ioasid_data;
+
+	ioasid_data = xa_erase(&default_allocator.xa, ioasid);
+	kfree_rcu(ioasid_data, rcu);
+}
+
+/* Allocate and initialize a new custom allocator with its helper functions */
+static struct ioasid_allocator_data *ioasid_alloc_allocator(struct ioasid_allocator_ops *ops)
+{
+	struct ioasid_allocator_data *ia_data;
+
+	ia_data = kzalloc(sizeof(*ia_data), GFP_ATOMIC);
+	if (!ia_data)
+		return NULL;
+
+	xa_init_flags(&ia_data->xa, XA_FLAGS_ALLOC);
+	INIT_LIST_HEAD(&ia_data->slist);
+	ia_data->flags |= IOASID_ALLOCATOR_CUSTOM;
+	ia_data->ops = ops;
+
+	/* For tracking custom allocators that share the same ops */
+	list_add_tail(&ops->list, &ia_data->slist);
+
+	return ia_data;
+}
+
+static bool use_same_ops(struct ioasid_allocator_ops *a, struct ioasid_allocator_ops *b)
+{
+	return (a->free == b->free) && (a->alloc == b->alloc);
+}
+
+/**
+ * ioasid_register_allocator - register a custom allocator
+ * @ops: the custom allocator ops to be registered
+ *
+ * Custom allocators take precedence over the default xarray based allocator.
+ * Private data associated with the IOASID allocated by the custom allocators
+ * are managed by IOASID framework similar to data stored in xa by default
+ * allocator.
+ *
+ * There can be multiple allocators registered but only one is active. In case
+ * of runtime removal of a custom allocator, the next one is activated based
+ * on the registration ordering.
+ *
+ * Multiple allocators can share the same alloc() function, in this case the
+ * IOASID space is shared.
+ */
+int ioasid_register_allocator(struct ioasid_allocator_ops *ops)
+{
+	struct ioasid_allocator_data *ia_data;
+	struct ioasid_allocator_data *pallocator;
+	int ret = 0;
+
+	spin_lock(&ioasid_allocator_lock);
+
+	ia_data = ioasid_alloc_allocator(ops);
+	if (!ia_data) {
+		ret = -ENOMEM;
+		goto out_unlock;
+	}
+
+	/*
+	 * No particular preference, we activate the first one and keep
+	 * the later registered allocators in a list in case the first one gets
+	 * removed due to hotplug.
+	 */
+	if (list_empty(&allocators_list)) {
+		WARN_ON(active_allocator != &default_allocator);
+		/* Use this new allocator if default is not active */
+		if (xa_empty(&active_allocator->xa)) {
+			rcu_assign_pointer(active_allocator, ia_data);
+			list_add_tail(&ia_data->list, &allocators_list);
+			goto out_unlock;
+		}
+		pr_warn("Default allocator active with outstanding IOASID\n");
+		ret = -EAGAIN;
+		goto out_free;
+	}
+
+	/* Check if the allocator is already registered */
+	list_for_each_entry(pallocator, &allocators_list, list) {
+		if (pallocator->ops == ops) {
+			pr_err("IOASID allocator already registered\n");
+			ret = -EEXIST;
+			goto out_free;
+		} else if (use_same_ops(pallocator->ops, ops)) {
+			/*
+			 * If the new allocator shares the same ops,
+			 * then they will share the same IOASID space.
+			 * We should put them under the same xarray.
+			 */
+			list_add_tail(&ops->list, &pallocator->slist);
+			goto out_free;
+		}
+	}
+	list_add_tail(&ia_data->list, &allocators_list);
+
+	spin_unlock(&ioasid_allocator_lock);
+	return 0;
+out_free:
+	kfree(ia_data);
+out_unlock:
+	spin_unlock(&ioasid_allocator_lock);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(ioasid_register_allocator);
+
+/**
+ * ioasid_unregister_allocator - Remove a custom IOASID allocator ops
+ * @ops: the custom allocator to be removed
+ *
+ * Remove an allocator from the list, activate the next allocator in
+ * the order it was registered. Or revert to default allocator if all
+ * custom allocators are unregistered without outstanding IOASIDs.
+ */
+void ioasid_unregister_allocator(struct ioasid_allocator_ops *ops)
+{
+	struct ioasid_allocator_data *pallocator;
+	struct ioasid_allocator_ops *sops;
+
+	spin_lock(&ioasid_allocator_lock);
+	if (list_empty(&allocators_list)) {
+		pr_warn("No custom IOASID allocators active!\n");
+		goto exit_unlock;
+	}
+
+	list_for_each_entry(pallocator, &allocators_list, list) {
+		if (!use_same_ops(pallocator->ops, ops))
+			continue;
+
+		if (list_is_singular(&pallocator->slist)) {
+			/* No shared helper functions */
+			list_del(&pallocator->list);
+			/*
+			 * All IOASIDs should have been freed before
+			 * the last allocator that shares the same ops
+			 * is unregistered.
+			 */
+			WARN_ON(!xa_empty(&pallocator->xa));
+			if (list_empty(&allocators_list)) {
+				pr_info("No custom IOASID allocators, switch to default.\n");
+				rcu_assign_pointer(active_allocator, &default_allocator);
+			} else if (pallocator == active_allocator) {
+				rcu_assign_pointer(active_allocator,
+						list_first_entry(&allocators_list,
+								struct ioasid_allocator_data, list));
+				pr_info("IOASID allocator changed");
+			}
+			kfree_rcu(pallocator, rcu);
+			break;
+		}
+		/*
+		 * Find the matching shared ops to delete,
+		 * but keep outstanding IOASIDs
+		 */
+		list_for_each_entry(sops, &pallocator->slist, list) {
+			if (sops == ops) {
+				list_del(&ops->list);
+				break;
+			}
+		}
+		break;
+	}
+
+exit_unlock:
+	spin_unlock(&ioasid_allocator_lock);
+}
+EXPORT_SYMBOL_GPL(ioasid_unregister_allocator);
+
+/**
+ * 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;
+
+	spin_lock(&ioasid_allocator_lock);
+	ioasid_data = xa_load(&active_allocator->xa, ioasid);
+	if (ioasid_data)
+		rcu_assign_pointer(ioasid_data->private, data);
+	else
+		ret = -ENOENT;
+	spin_unlock(&ioasid_allocator_lock);
+
+	/*
+	 * 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)
+{
+	struct ioasid_data *data;
+	void *adata;
+	ioasid_t id;
+
+	data = kzalloc(sizeof(*data), GFP_ATOMIC);
+	if (!data)
+		return INVALID_IOASID;
+
+	data->set = set;
+	data->private = private;
+
+	/*
+	 * Custom allocator needs allocator data to perform platform specific
+	 * operations.
+	 */
+	spin_lock(&ioasid_allocator_lock);
+	adata = active_allocator->flags & IOASID_ALLOCATOR_CUSTOM ? active_allocator->ops->pdata : data;
+	id = active_allocator->ops->alloc(min, max, adata);
+	if (id == INVALID_IOASID) {
+		pr_err("Failed ASID allocation %lu\n", active_allocator->flags);
+		goto exit_free;
+	}
+
+	if ((active_allocator->flags & IOASID_ALLOCATOR_CUSTOM) &&
+	     xa_alloc(&active_allocator->xa, &id, data, XA_LIMIT(id, id), GFP_ATOMIC)) {
+		/* Custom allocator needs framework to store and track allocation results */
+		pr_err("Failed to alloc ioasid from %d\n", id);
+		active_allocator->ops->free(id, active_allocator->ops->pdata);
+		goto exit_free;
+	}
+	data->id = id;
+
+	spin_unlock(&ioasid_allocator_lock);
+	return id;
+exit_free:
+	spin_unlock(&ioasid_allocator_lock);
+	kfree(data);
+	return INVALID_IOASID;
+}
+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;
+
+	spin_lock(&ioasid_allocator_lock);
+	ioasid_data = xa_load(&active_allocator->xa, ioasid);
+	if (!ioasid_data) {
+		pr_err("Trying to free unknown IOASID %u\n", ioasid);
+		goto exit_unlock;
+	}
+
+	active_allocator->ops->free(ioasid, active_allocator->ops->pdata);
+	/* Custom allocator needs additional steps to free the xa element */
+	if (active_allocator->flags & IOASID_ALLOCATOR_CUSTOM) {
+		ioasid_data = xa_erase(&active_allocator->xa, ioasid);
+		kfree_rcu(ioasid_data, rcu);
+	}
+
+exit_unlock:
+	spin_unlock(&ioasid_allocator_lock);
+}
+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 exists, 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 if @set is not NULL and the IOASID does not belong to the set.
+ */
+void *ioasid_find(struct ioasid_set *set, ioasid_t ioasid,
+		  bool (*getter)(void *))
+{
+	void *priv;
+	struct ioasid_data *ioasid_data;
+	struct ioasid_allocator_data *idata;
+
+	rcu_read_lock();
+	idata = rcu_dereference(active_allocator);
+	ioasid_data = xa_load(&idata->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_AUTHOR("Jean-Philippe Brucker <jean-philippe.brucker@arm.com>");
+MODULE_AUTHOR("Jacob Pan <jacob.jun.pan@linux.intel.com>");
+MODULE_DESCRIPTION("IO Address Space ID (IOASID) allocator");
+MODULE_LICENSE("GPL");