[PATCH v3 05/15] iommupt: Add iova_to_phys op

[Jason Gunthorpe <jgg@nvidia.com>]

iova_to_phys is a performance path for the DMA API and iommufd, implement
it using an unrolled get_user_pages() like function waterfall scheme.

The implementation itself is fairly trivial.

Tested-by: Alejandro Jimenez <alejandro.j.jimenez@oracle.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
---
 drivers/iommu/generic_pt/iommu_pt.h | 105 ++++++++++++++++++++++++++++
 include/linux/generic_pt/iommu.h    |  34 +++++++--
 2 files changed, 134 insertions(+), 5 deletions(-)

diff --git a/drivers/iommu/generic_pt/iommu_pt.h b/drivers/iommu/generic_pt/iommu_pt.h
index 205c232bda68b5..bae87ff34b8043 100644
--- a/drivers/iommu/generic_pt/iommu_pt.h
+++ b/drivers/iommu/generic_pt/iommu_pt.h
@@ -17,6 +17,111 @@
 
 #define DOMAIN_NS(op) CONCATENATE(CONCATENATE(pt_iommu_, PTPFX), op)
 
+static int make_range_ul(struct pt_common *common, struct pt_range *range,
+			 unsigned long iova, unsigned long len)
+{
+	unsigned long last;
+
+	if (unlikely(len == 0))
+		return -EINVAL;
+
+	if (check_add_overflow(iova, len - 1, &last))
+		return -EOVERFLOW;
+
+	*range = pt_make_range(common, iova, last);
+	if (sizeof(iova) > sizeof(range->va)) {
+		if (unlikely(range->va != iova || range->last_va != last))
+			return -EOVERFLOW;
+	}
+	return 0;
+}
+
+static __maybe_unused int make_range_u64(struct pt_common *common,
+					 struct pt_range *range, u64 iova,
+					 u64 len)
+{
+	if (unlikely(iova > ULONG_MAX || len > ULONG_MAX))
+		return -EOVERFLOW;
+	return make_range_ul(common, range, iova, len);
+}
+
+/*
+ * Some APIs use unsigned long some use dma_addr_t as the type. Dispatch to the
+ * correct validation based on the type.
+ */
+#define make_range_no_check(common, range, iova, len)                   \
+	({                                                              \
+		int ret;                                                \
+		if (sizeof(iova) > sizeof(unsigned long) ||             \
+		    sizeof(len) > sizeof(unsigned long))                \
+			ret = make_range_u64(common, range, iova, len); \
+		else                                                    \
+			ret = make_range_ul(common, range, iova, len);  \
+		ret;                                                    \
+	})
+
+#define make_range(common, range, iova, len)                             \
+	({                                                               \
+		int ret = make_range_no_check(common, range, iova, len); \
+		if (!ret)                                                \
+			ret = pt_check_range(range);                     \
+		ret;                                                     \
+	})
+
+static __always_inline int __do_iova_to_phys(struct pt_range *range, void *arg,
+					     unsigned int level,
+					     struct pt_table_p *table,
+					     pt_level_fn_t descend_fn)
+{
+	struct pt_state pts = pt_init(range, level, table);
+	pt_oaddr_t *res = arg;
+
+	switch (pt_load_single_entry(&pts)) {
+	case PT_ENTRY_EMPTY:
+		return -ENOENT;
+	case PT_ENTRY_TABLE:
+		return pt_descend(&pts, arg, descend_fn);
+	case PT_ENTRY_OA:
+		*res = pt_entry_oa_full(&pts);
+		return 0;
+	}
+	return -ENOENT;
+}
+PT_MAKE_LEVELS(__iova_to_phys, __do_iova_to_phys);
+
+/**
+ * iova_to_phys() - Return the output address for the given IOVA
+ * @iommu_table: Table to query
+ * @iova: IO virtual address to query
+ *
+ * Determine the output address from the given IOVA. @iova may have any
+ * alignment, the returned physical will be adjusted with any sub page offset.
+ *
+ * Context: The caller must hold a read range lock that includes @iova.
+ *
+ * Return: 0 if there is no translation for the given iova.
+ */
+phys_addr_t DOMAIN_NS(iova_to_phys)(struct iommu_domain *domain,
+				    dma_addr_t iova)
+{
+	struct pt_iommu *iommu_table =
+		container_of(domain, struct pt_iommu, domain);
+	struct pt_range range;
+	pt_oaddr_t res;
+	int ret;
+
+	ret = make_range(common_from_iommu(iommu_table), &range, iova, 1);
+	if (ret)
+		return ret;
+
+	ret = pt_walk_range(&range, __iova_to_phys, &res);
+	/* PHYS_ADDR_MAX would be a better error code */
+	if (ret)
+		return 0;
+	return res;
+}
+EXPORT_SYMBOL_NS_GPL(DOMAIN_NS(iova_to_phys), "GENERIC_PT_IOMMU");
+
 struct pt_iommu_collect_args {
 	struct iommu_pages_list free_list;
 	u8 ignore_mapped : 1;
diff --git a/include/linux/generic_pt/iommu.h b/include/linux/generic_pt/iommu.h
index b51de39c03c431..1fe5106997f833 100644
--- a/include/linux/generic_pt/iommu.h
+++ b/include/linux/generic_pt/iommu.h
@@ -116,11 +116,13 @@ struct pt_iommu_cfg {
 };
 
 /* Generate the exported function signatures from iommu_pt.h */
-#define IOMMU_PROTOTYPES(fmt)                                             \
-	int pt_iommu_##fmt##_init(struct pt_iommu_##fmt *table,           \
-				  const struct pt_iommu_##fmt##_cfg *cfg, \
-				  gfp_t gfp);                             \
-	void pt_iommu_##fmt##_hw_info(struct pt_iommu_##fmt *table,       \
+#define IOMMU_PROTOTYPES(fmt)                                                  \
+	phys_addr_t pt_iommu_##fmt##_iova_to_phys(struct iommu_domain *domain, \
+						  dma_addr_t iova);            \
+	int pt_iommu_##fmt##_init(struct pt_iommu_##fmt *table,                \
+				  const struct pt_iommu_##fmt##_cfg *cfg,      \
+				  gfp_t gfp);                                  \
+	void pt_iommu_##fmt##_hw_info(struct pt_iommu_##fmt *table,            \
 				      struct pt_iommu_##fmt##_hw_info *info)
 #define IOMMU_FORMAT(fmt, member)       \
 	struct pt_iommu_##fmt {         \
@@ -129,6 +131,28 @@ struct pt_iommu_cfg {
 	};                              \
 	IOMMU_PROTOTYPES(fmt)
 
+/*
+ * A driver uses IOMMU_PT_DOMAIN_OPS to populate the iommu_domain_ops for the
+ * iommu_pt
+ */
+#define IOMMU_PT_DOMAIN_OPS(fmt) \
+	.iova_to_phys = &pt_iommu_##fmt##_iova_to_phys,
+
+/*
+ * The driver should setup its domain struct like
+ *	union {
+ *		struct iommu_domain domain;
+ *		struct pt_iommu_xxx xx;
+ *	};
+ * PT_IOMMU_CHECK_DOMAIN(struct mock_iommu_domain, xx.iommu, domain);
+ *
+ * Which creates an alias between driver_domain.domain and
+ * driver_domain.xx.iommu.domain. This is to avoid a mass rename of existing
+ * driver_domain.domain users.
+ */
+#define PT_IOMMU_CHECK_DOMAIN(s, pt_iommu_memb, domain_memb) \
+	static_assert(offsetof(s, pt_iommu_memb.domain) ==   \
+		      offsetof(s, domain_memb))
 
 struct pt_iommu_amdv1_cfg {
 	struct pt_iommu_cfg common;
-- 
2.43.0