BACKPORT: FROMLIST: iommu/io-pgtable: Add configure() operation

Allow IOMMU drivers to create the io-pgtable configuration without
allocating any tables. This will be used by the SMMUv3-KVM driver to
initialize a config and pass it to KVM.

Link: https://lore.kernel.org/all/20241212180423.1578358-4-smostafa@google.com/

Bug: 357781595
Bug: 384432312

Change-Id: I6e6aed0f7e2c57d07bd15519569a886d07330e60
Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
Signed-off-by: Mostafa Saleh <smostafa@google.com>

drivers/iommu/io-pgtable-arm.c

@@ -194,6 +194,13 @@ out_free_data:
 	return NULL;
 }
 
+static int arm_64_lpae_configure_s1(struct io_pgtable_cfg *cfg)
+{
+	struct arm_lpae_io_pgtable data = {};
+
+	return arm_lpae_init_pgtable_s1(cfg, &data);
+}
+
 static struct io_pgtable *
 arm_64_lpae_alloc_pgtable_s2(struct io_pgtable_cfg *cfg, void *cookie)
 {
@@ -225,6 +232,13 @@ out_free_data:
 	return NULL;
 }
 
+static int arm_64_lpae_configure_s2(struct io_pgtable_cfg *cfg)
+{
+	struct arm_lpae_io_pgtable data = {};
+
+	return arm_lpae_init_pgtable_s2(cfg, &data);
+}
+
 static struct io_pgtable *
 arm_32_lpae_alloc_pgtable_s1(struct io_pgtable_cfg *cfg, void *cookie)
 {
@@ -312,12 +326,14 @@ struct io_pgtable_init_fns io_pgtable_arm_64_lpae_s1_init_fns = {
 	.caps	= IO_PGTABLE_CAP_CUSTOM_ALLOCATOR,
 	.alloc	= arm_64_lpae_alloc_pgtable_s1,
 	.free	= arm_lpae_free_pgtable,
+	.configure	= arm_64_lpae_configure_s1,
 };
 
 struct io_pgtable_init_fns io_pgtable_arm_64_lpae_s2_init_fns = {
 	.caps	= IO_PGTABLE_CAP_CUSTOM_ALLOCATOR,
 	.alloc	= arm_64_lpae_alloc_pgtable_s2,
 	.free	= arm_lpae_free_pgtable,
+	.configure	= arm_64_lpae_configure_s2,
 };
 
 struct io_pgtable_init_fns io_pgtable_arm_32_lpae_s1_init_fns = {

drivers/iommu/io-pgtable.c

@@ -99,3 +99,18 @@ void free_io_pgtable_ops(struct io_pgtable_ops *ops)
 	io_pgtable_init_table[iop->fmt]->free(iop);
 }
 EXPORT_SYMBOL_GPL(free_io_pgtable_ops);
+
+int io_pgtable_configure(struct io_pgtable_cfg *cfg)
+{
+	const struct io_pgtable_init_fns *fns;
+
+	if (cfg->fmt >= IO_PGTABLE_NUM_FMTS)
+		return -EINVAL;
+
+	fns = io_pgtable_init_table[cfg->fmt];
+	if (!fns || !fns->configure)
+		return -EOPNOTSUPP;
+
+	return fns->configure(cfg);
+}
+EXPORT_SYMBOL_GPL(io_pgtable_configure);

include/linux/io-pgtable.h

@@ -49,6 +49,7 @@ struct iommu_flush_ops {
 /**
  * struct io_pgtable_cfg - Configuration data for a set of page tables.
  *
+ * @fmt:	       Format used for these page tables
  * @quirks:        A bitmap of hardware quirks that require some special
  *                 action by the low-level page table allocator.
  * @pgsize_bitmap: A bitmap of page sizes supported by this set of page
@@ -62,6 +63,7 @@ struct iommu_flush_ops {
  *                 page table walker.
  */
 struct io_pgtable_cfg {
+	enum io_pgtable_fmt		fmt;
 	/*
 	 * IO_PGTABLE_QUIRK_ARM_NS: (ARM formats) Set NS and NSTABLE bits in
 	 *	stage 1 PTEs, for hardware which insists on validating them
@@ -241,6 +243,17 @@ struct io_pgtable_ops *alloc_io_pgtable_ops(enum io_pgtable_fmt fmt,
  */
 void free_io_pgtable_ops(struct io_pgtable_ops *ops);
 
+/**
+ * io_pgtable_configure - Create page table config
+ *
+ * @cfg:	The page table configuration.
+ *
+ * Initialize @cfg in the same way as alloc_io_pgtable_ops(), without allocating
+ * anything.
+ *
+ * Not all io_pgtable drivers implement this operation.
+ */
+int io_pgtable_configure(struct io_pgtable_cfg *cfg);
 
 /*
  * Internal structures for page table allocator implementations.
@@ -301,11 +314,13 @@ enum io_pgtable_caps {
  *
  * @alloc: Allocate a set of page tables described by cfg.
  * @free:  Free the page tables associated with iop.
+ * @configure: Create the configuration without allocating anything. Optional.
  * @caps:  Combination of @io_pgtable_caps flags encoding the backend capabilities.
  */
 struct io_pgtable_init_fns {
 	struct io_pgtable *(*alloc)(struct io_pgtable_cfg *cfg, void *cookie);
 	void (*free)(struct io_pgtable *iop);
+	int (*configure)(struct io_pgtable_cfg *cfg);
 	u32 caps;
 };