[PATCH v2 1/7] iommu/io-pgtable: Introduce dynamic io-pgtable fmt registration

[Isaac J. Manjarres]

The io-pgtable code constructs an array of init functions for each
page table format at compile time. This is not ideal, as this
increases the footprint of the io-pgtable code, as well as prevents
io-pgtable formats from being built as kernel modules.

In preparation for modularizing the io-pgtable formats, switch to a
dynamic registration scheme, where each io-pgtable format can register
their init functions with the io-pgtable code at boot or module
insertion time.

Signed-off-by: Isaac J. Manjarres <isaacm@xxxxxxxxxxxxxx>
---
 drivers/iommu/io-pgtable-arm-v7s.c | 34 +++++++++++++-
 drivers/iommu/io-pgtable-arm.c     | 90 ++++++++++++++++++++++++++----------
 drivers/iommu/io-pgtable.c         | 94 ++++++++++++++++++++++++++++++++------
 include/linux/io-pgtable.h         | 51 +++++++++++++--------
 4 files changed, 209 insertions(+), 60 deletions(-)

diff --git a/drivers/iommu/io-pgtable-arm-v7s.c b/drivers/iommu/io-pgtable-arm-v7s.c
index 1d92ac9..89aad2f 100644
--- a/drivers/iommu/io-pgtable-arm-v7s.c
+++ b/drivers/iommu/io-pgtable-arm-v7s.c
@@ -28,6 +28,7 @@
 #include <linux/iommu.h>
 #include <linux/kernel.h>
 #include <linux/kmemleak.h>
+#include <linux/module.h>
 #include <linux/sizes.h>
 #include <linux/slab.h>
 #include <linux/spinlock.h>
@@ -835,7 +836,8 @@ static struct io_pgtable *arm_v7s_alloc_pgtable(struct io_pgtable_cfg *cfg,
 	return NULL;
 }
 
-struct io_pgtable_init_fns io_pgtable_arm_v7s_init_fns = {
+static struct io_pgtable_init_fns io_pgtable_arm_v7s_init_fns = {
+	.fmt	= ARM_V7S,
 	.alloc	= arm_v7s_alloc_pgtable,
 	.free	= arm_v7s_free_pgtable,
 };
@@ -982,5 +984,33 @@ static int __init arm_v7s_do_selftests(void)
 	pr_info("self test ok\n");
 	return 0;
 }
-subsys_initcall(arm_v7s_do_selftests);
+#else
+static int arm_v7s_do_selftests(void)
+{
+	return 0;
+}
 #endif
+
+static int __init arm_v7s_init(void)
+{
+	int ret;
+
+	ret = io_pgtable_ops_register(&io_pgtable_arm_v7s_init_fns);
+	if (ret < 0) {
+		pr_err("Failed to register ARM V7S format\n");
+		return ret;
+	}
+
+	ret = arm_v7s_do_selftests();
+	if (ret < 0)
+		io_pgtable_ops_unregister(&io_pgtable_arm_v7s_init_fns);
+
+	return ret;
+}
+core_initcall(arm_v7s_init);
+
+static void __exit arm_v7s_exit(void)
+{
+	io_pgtable_ops_unregister(&io_pgtable_arm_v7s_init_fns);
+}
+module_exit(arm_v7s_exit);
diff --git a/drivers/iommu/io-pgtable-arm.c b/drivers/iommu/io-pgtable-arm.c
index 87def58..ff0ea2f 100644
--- a/drivers/iommu/io-pgtable-arm.c
+++ b/drivers/iommu/io-pgtable-arm.c
@@ -13,6 +13,7 @@
 #include <linux/bitops.h>
 #include <linux/io-pgtable.h>
 #include <linux/kernel.h>
+#include <linux/module.h>
 #include <linux/sizes.h>
 #include <linux/slab.h>
 #include <linux/types.h>
@@ -1043,29 +1044,32 @@ arm_mali_lpae_alloc_pgtable(struct io_pgtable_cfg *cfg, void *cookie)
 	return NULL;
 }
 
-struct io_pgtable_init_fns io_pgtable_arm_64_lpae_s1_init_fns = {
-	.alloc	= arm_64_lpae_alloc_pgtable_s1,
-	.free	= arm_lpae_free_pgtable,
-};
-
-struct io_pgtable_init_fns io_pgtable_arm_64_lpae_s2_init_fns = {
-	.alloc	= arm_64_lpae_alloc_pgtable_s2,
-	.free	= arm_lpae_free_pgtable,
-};
-
-struct io_pgtable_init_fns io_pgtable_arm_32_lpae_s1_init_fns = {
-	.alloc	= arm_32_lpae_alloc_pgtable_s1,
-	.free	= arm_lpae_free_pgtable,
-};
-
-struct io_pgtable_init_fns io_pgtable_arm_32_lpae_s2_init_fns = {
-	.alloc	= arm_32_lpae_alloc_pgtable_s2,
-	.free	= arm_lpae_free_pgtable,
-};
-
-struct io_pgtable_init_fns io_pgtable_arm_mali_lpae_init_fns = {
-	.alloc	= arm_mali_lpae_alloc_pgtable,
-	.free	= arm_lpae_free_pgtable,
+static struct io_pgtable_init_fns io_pgtable_arm_lpae_init_fns[] = {
+	{
+		.fmt	= ARM_32_LPAE_S1,
+		.alloc	= arm_32_lpae_alloc_pgtable_s1,
+		.free	= arm_lpae_free_pgtable,
+	},
+	{
+		.fmt	= ARM_32_LPAE_S2,
+		.alloc	= arm_32_lpae_alloc_pgtable_s2,
+		.free	= arm_lpae_free_pgtable,
+	},
+	{
+		.fmt	= ARM_64_LPAE_S1,
+		.alloc	= arm_64_lpae_alloc_pgtable_s1,
+		.free	= arm_lpae_free_pgtable,
+	},
+	{
+		.fmt	= ARM_64_LPAE_S2,
+		.alloc	= arm_64_lpae_alloc_pgtable_s2,
+		.free	= arm_lpae_free_pgtable,
+	},
+	{
+		.fmt	= ARM_MALI_LPAE,
+		.alloc	= arm_mali_lpae_alloc_pgtable,
+		.free	= arm_lpae_free_pgtable,
+	},
 };
 
 #ifdef CONFIG_IOMMU_IO_PGTABLE_LPAE_SELFTEST
@@ -1250,5 +1254,43 @@ static int __init arm_lpae_do_selftests(void)
 	pr_info("selftest: completed with %d PASS %d FAIL\n", pass, fail);
 	return fail ? -EFAULT : 0;
 }
-subsys_initcall(arm_lpae_do_selftests);
+#else
+static int __init arm_lpae_do_selftests(void)
+{
+	return 0;
+}
 #endif
+
+static int __init arm_lpae_init(void)
+{
+	int ret, i;
+
+	for (i = 0; i < ARRAY_SIZE(io_pgtable_arm_lpae_init_fns); i++) {
+		ret = io_pgtable_ops_register(&io_pgtable_arm_lpae_init_fns[i]);
+		if (ret < 0) {
+			pr_err("Failed to register ARM LPAE fmt: %d\n");
+			goto err_io_pgtable_register;
+		}
+	}
+
+	ret = arm_lpae_do_selftests();
+	if (ret < 0)
+		goto err_io_pgtable_register;
+
+	return 0;
+
+err_io_pgtable_register:
+	for (i = i - 1; i >= 0; i--)
+		io_pgtable_ops_unregister(&io_pgtable_arm_lpae_init_fns[i]);
+	return ret;
+}
+core_initcall(arm_lpae_init);
+
+static void __exit arm_lpae_exit(void)
+{
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(io_pgtable_arm_lpae_init_fns); i++)
+		io_pgtable_ops_unregister(&io_pgtable_arm_lpae_init_fns[i]);
+}
+module_exit(arm_lpae_exit);
diff --git a/drivers/iommu/io-pgtable.c b/drivers/iommu/io-pgtable.c
index 94394c8..2c6eb2e 100644
--- a/drivers/iommu/io-pgtable.c
+++ b/drivers/iommu/io-pgtable.c
@@ -10,33 +10,45 @@
 #include <linux/bug.h>
 #include <linux/io-pgtable.h>
 #include <linux/kernel.h>
+#include <linux/rwlock.h>
+#include <linux/slab.h>
 #include <linux/types.h>
 
-static const struct io_pgtable_init_fns *
-io_pgtable_init_table[IO_PGTABLE_NUM_FMTS] = {
-#ifdef CONFIG_IOMMU_IO_PGTABLE_LPAE
-	[ARM_32_LPAE_S1] = &io_pgtable_arm_32_lpae_s1_init_fns,
-	[ARM_32_LPAE_S2] = &io_pgtable_arm_32_lpae_s2_init_fns,
-	[ARM_64_LPAE_S1] = &io_pgtable_arm_64_lpae_s1_init_fns,
-	[ARM_64_LPAE_S2] = &io_pgtable_arm_64_lpae_s2_init_fns,
-	[ARM_MALI_LPAE] = &io_pgtable_arm_mali_lpae_init_fns,
-#endif
-#ifdef CONFIG_IOMMU_IO_PGTABLE_ARMV7S
-	[ARM_V7S] = &io_pgtable_arm_v7s_init_fns,
-#endif
+struct io_pgtable_init_fns_node {
+	struct io_pgtable_init_fns *fns;
+	struct list_head list;
 };
 
+static LIST_HEAD(io_pgtable_init_fns_list);
+static DEFINE_RWLOCK(io_pgtable_init_fns_list_lock);
+
+static struct io_pgtable_init_fns *io_pgtable_get_init_fns(enum io_pgtable_fmt fmt)
+{
+	struct io_pgtable_init_fns_node *iter;
+	struct io_pgtable_init_fns *fns = NULL;
+
+	read_lock(&io_pgtable_init_fns_list_lock);
+	list_for_each_entry(iter, &io_pgtable_init_fns_list, list)
+		if (iter->fns->fmt == fmt) {
+			fns = iter->fns;
+			break;
+		}
+	read_unlock(&io_pgtable_init_fns_list_lock);
+
+	return fns;
+}
+
 struct io_pgtable_ops *alloc_io_pgtable_ops(enum io_pgtable_fmt fmt,
 					    struct io_pgtable_cfg *cfg,
 					    void *cookie)
 {
 	struct io_pgtable *iop;
-	const struct io_pgtable_init_fns *fns;
+	struct io_pgtable_init_fns *fns;
 
 	if (fmt >= IO_PGTABLE_NUM_FMTS)
 		return NULL;
 
-	fns = io_pgtable_init_table[fmt];
+	fns = io_pgtable_get_init_fns(fmt);
 	if (!fns)
 		return NULL;
 
@@ -59,12 +71,64 @@ EXPORT_SYMBOL_GPL(alloc_io_pgtable_ops);
 void free_io_pgtable_ops(struct io_pgtable_ops *ops)
 {
 	struct io_pgtable *iop;
+	struct io_pgtable_init_fns *fns;
 
 	if (!ops)
 		return;
 
 	iop = io_pgtable_ops_to_pgtable(ops);
 	io_pgtable_tlb_flush_all(iop);
-	io_pgtable_init_table[iop->fmt]->free(iop);
+	fns = io_pgtable_get_init_fns(iop->fmt);
+	if (fns)
+		fns->free(iop);
 }
 EXPORT_SYMBOL_GPL(free_io_pgtable_ops);
+
+int io_pgtable_ops_register(struct io_pgtable_init_fns *init_fns)
+{
+	struct io_pgtable_init_fns_node *iter, *fns_node;
+	int ret = 0;
+
+	if (!init_fns || init_fns->fmt >= IO_PGTABLE_NUM_FMTS ||
+	    !init_fns->alloc || !init_fns->free)
+		return -EINVAL;
+
+	fns_node = kzalloc(sizeof(*fns_node), GFP_KERNEL);
+	if (!fns_node)
+		return -ENOMEM;
+
+	write_lock(&io_pgtable_init_fns_list_lock);
+	list_for_each_entry(iter, &io_pgtable_init_fns_list, list)
+		if (iter->fns->fmt == init_fns->fmt) {
+			ret = -EEXIST;
+			kfree(fns_node);
+			break;
+		}
+
+	if (!ret) {
+		fns_node->fns = init_fns;
+		INIT_LIST_HEAD(&fns_node->list);
+		list_add_tail(&fns_node->list, &io_pgtable_init_fns_list);
+	}
+	write_unlock(&io_pgtable_init_fns_list_lock);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(io_pgtable_ops_register);
+
+void io_pgtable_ops_unregister(struct io_pgtable_init_fns *init_fns)
+{
+	struct io_pgtable_init_fns_node *iter, *tmp;
+
+	if (!init_fns)
+		return;
+
+	write_lock(&io_pgtable_init_fns_list_lock);
+	list_for_each_entry_safe(iter, tmp, &io_pgtable_init_fns_list, list)
+		if (iter->fns == init_fns) {
+			list_del(&iter->list);
+			kfree(iter);
+			break;
+		}
+	write_unlock(&io_pgtable_init_fns_list_lock);
+}
+EXPORT_SYMBOL_GPL(io_pgtable_ops_unregister);
diff --git a/include/linux/io-pgtable.h b/include/linux/io-pgtable.h
index ea727eb..45b367ce 100644
--- a/include/linux/io-pgtable.h
+++ b/include/linux/io-pgtable.h
@@ -163,6 +163,38 @@ struct io_pgtable_ops {
 };
 
 /**
+ * struct io_pgtable_init_fns - Alloc/free a set of page tables for a
+ *                              particular format.
+ *
+ * @fmt:   The page table format.
+ * @alloc: Allocate a set of page tables described by cfg.
+ * @free:  Free the page tables associated with iop.
+ */
+struct io_pgtable_init_fns {
+	enum io_pgtable_fmt fmt;
+	struct io_pgtable *(*alloc)(struct io_pgtable_cfg *cfg, void *cookie);
+	void (*free)(struct io_pgtable *iop);
+};
+
+/**
+ * io_pgtable_ops_register() - Register the page table routines for a page table
+ *                             format.
+ *
+ * @init_fns: The functions for allocating and freeing the page tables of
+ *            a particular format.
+ */
+int io_pgtable_ops_register(struct io_pgtable_init_fns *init_fns);
+
+/**
+ * io_pgtable_ops_unregister() - Unregister the page table routines for a page
+ *                               table format.
+ *
+ * @init_fns: The functions for allocating and freeing the page tables of
+ *            a particular format.
+ */
+void io_pgtable_ops_unregister(struct io_pgtable_init_fns *init_fns);
+
+/**
  * alloc_io_pgtable_ops() - Allocate a page table allocator for use by an IOMMU.
  *
  * @fmt:    The page table format.
@@ -233,23 +265,4 @@ io_pgtable_tlb_add_page(struct io_pgtable *iop,
 		iop->cfg.tlb->tlb_add_page(gather, iova, granule, iop->cookie);
 }
 
-/**
- * struct io_pgtable_init_fns - Alloc/free a set of page tables for a
- *                              particular format.
- *
- * @alloc: Allocate a set of page tables described by cfg.
- * @free:  Free the page tables associated with iop.
- */
-struct io_pgtable_init_fns {
-	struct io_pgtable *(*alloc)(struct io_pgtable_cfg *cfg, void *cookie);
-	void (*free)(struct io_pgtable *iop);
-};
-
-extern struct io_pgtable_init_fns io_pgtable_arm_32_lpae_s1_init_fns;
-extern struct io_pgtable_init_fns io_pgtable_arm_32_lpae_s2_init_fns;
-extern struct io_pgtable_init_fns io_pgtable_arm_64_lpae_s1_init_fns;
-extern struct io_pgtable_init_fns io_pgtable_arm_64_lpae_s2_init_fns;
-extern struct io_pgtable_init_fns io_pgtable_arm_v7s_init_fns;
-extern struct io_pgtable_init_fns io_pgtable_arm_mali_lpae_init_fns;
-
 #endif /* __IO_PGTABLE_H */
-- 
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