[PATCH 4/3] iommu/io-pgtable: Rationalise quirk handling

[Robin Murphy]

As the number of io-pgtable implementations grows beyond 1, it's time
to rationalise the quirks mechanism before things have a chance to
start getting really ugly and out-of-hand.

To that end:
- Indicate exactly which quirks each format can/does support.
- Fail creating a table if a caller wants unsupported quirks.
- Properly document where each quirk applies and why.

Signed-off-by: Robin Murphy <robin.murphy at arm.com>
---
 drivers/iommu/io-pgtable-arm-v7s.c |  3 +++
 drivers/iommu/io-pgtable-arm.c     |  2 ++
 drivers/iommu/io-pgtable.c         |  3 +++
 drivers/iommu/io-pgtable.h         | 24 ++++++++++++++++++++----
 4 files changed, 28 insertions(+), 4 deletions(-)

diff --git a/drivers/iommu/io-pgtable-arm-v7s.c b/drivers/iommu/io-pgtable-arm-v7s.c
index d39a021..9bc607a 100644
--- a/drivers/iommu/io-pgtable-arm-v7s.c
+++ b/drivers/iommu/io-pgtable-arm-v7s.c
@@ -690,6 +690,9 @@ out_free_data:
 struct io_pgtable_init_fns io_pgtable_arm_v7s_init_fns = {
 	.alloc	= arm_v7s_alloc_pgtable,
 	.free	= arm_v7s_free_pgtable,
+	.supported_quirks = IO_PGTABLE_QUIRK_ARM_NS |
+			    IO_PGTABLE_QUIRK_NO_PERMS |
+			    IO_PGTABLE_QUIRK_TLBI_ON_MAP,
 };
 
 #ifdef CONFIG_IOMMU_IO_PGTABLE_ARMV7S_SELFTEST
diff --git a/drivers/iommu/io-pgtable-arm.c b/drivers/iommu/io-pgtable-arm.c
index 4095af2..32f94f1 100644
--- a/drivers/iommu/io-pgtable-arm.c
+++ b/drivers/iommu/io-pgtable-arm.c
@@ -863,6 +863,7 @@ arm_32_lpae_alloc_pgtable_s2(struct io_pgtable_cfg *cfg, void *cookie)
 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,
+	.supported_quirks = IO_PGTABLE_QUIRK_ARM_NS,
 };
 
 struct io_pgtable_init_fns io_pgtable_arm_64_lpae_s2_init_fns = {
@@ -873,6 +874,7 @@ struct io_pgtable_init_fns io_pgtable_arm_64_lpae_s2_init_fns = {
 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,
+	.supported_quirks = IO_PGTABLE_QUIRK_ARM_NS,
 };
 
 struct io_pgtable_init_fns io_pgtable_arm_32_lpae_s2_init_fns = {
diff --git a/drivers/iommu/io-pgtable.c b/drivers/iommu/io-pgtable.c
index 876f6a7..0f57a45 100644
--- a/drivers/iommu/io-pgtable.c
+++ b/drivers/iommu/io-pgtable.c
@@ -52,6 +52,9 @@ struct io_pgtable_ops *alloc_io_pgtable_ops(enum io_pgtable_fmt fmt,
 	if (!fns)
 		return NULL;
 
+	if (cfg->quirks & ~fns->supported_quirks)
+		return NULL;
+
 	iop = fns->alloc(cfg, cookie);
 	if (!iop)
 		return NULL;
diff --git a/drivers/iommu/io-pgtable.h b/drivers/iommu/io-pgtable.h
index 4faee7d..6e7f11e 100644
--- a/drivers/iommu/io-pgtable.h
+++ b/drivers/iommu/io-pgtable.h
@@ -47,10 +47,24 @@ struct iommu_gather_ops {
  *                 page table walker.
  */
 struct io_pgtable_cfg {
-	#define IO_PGTABLE_QUIRK_ARM_NS		BIT(0) /* Set NS bit in PTEs */
-	#define IO_PGTABLE_QUIRK_NO_PERMS	BIT(1) /* No AP/XN bits */
-	#define IO_PGTABLE_QUIRK_TLBI_ON_MAP	BIT(2) /* TLB Inv. on map */
-	int				quirks;
+	/*
+	 * IO_PGTABLE_QUIRK_ARM_NS: (ARM formats) Set NS and NSTABLE bits in
+	 *	stage 1 PTEs, for hardware which insists on validating them
+	 *	even in	non-secure state where they should normally be ignored.
+	 *
+	 * IO_PGTABLE_QUIRK_NO_PERMS: Ignore the IOMMU_READ, IOMMU_WRITE and
+	 *	IOMMU_NOEXEC flags and map everything with full access, for
+	 *	hardware which does not implement the permissions of a given
+	 *	format, and/or requires some format-specific default value.
+	 *
+	 * IO_PGTABLE_QUIRK_TLBI_ON_MAP: If the format forbids caching invalid
+	 *	(unmapped) entries but the hardware might do so anyway, perform
+	 *	TLB maintenance when mapping as well as when unmapping.
+	 */
+	#define IO_PGTABLE_QUIRK_ARM_NS		BIT(0)
+	#define IO_PGTABLE_QUIRK_NO_PERMS	BIT(1)
+	#define IO_PGTABLE_QUIRK_TLBI_ON_MAP	BIT(2)
+	unsigned int			quirks;
 	unsigned long			pgsize_bitmap;
 	unsigned int			ias;
 	unsigned int			oas;
@@ -173,10 +187,12 @@ static inline void io_pgtable_tlb_sync(struct io_pgtable *iop)
  *
  * @alloc: Allocate a set of page tables described by cfg.
  * @free:  Free the page tables associated with iop.
+ * @supported_quirks: Bitmap of quirks supported by the format.
  */
 struct io_pgtable_init_fns {
 	struct io_pgtable *(*alloc)(struct io_pgtable_cfg *cfg, void *cookie);
 	void (*free)(struct io_pgtable *iop);
+	unsigned int supported_quirks;
 };
 
 extern struct io_pgtable_init_fns io_pgtable_arm_32_lpae_s1_init_fns;
-- 
2.7.0.25.gfc10eb5.dirty