[PATCH 3/3] iommu/uapi: Add helper function for size lookup

[Jacob Pan <jacob.jun.pan@linux.intel.com>]

IOMMU UAPI can be extended in the future by adding new
fields at the end of each user data structure. Since we use
a unified UAPI version for compatibility checking, a lookup
function is needed to find the correct user data size to copy
from user.

This patch adds a helper function based on a 2D lookup with
version and type as input arguments.

Signed-off-by: Liu Yi L <yi.l.liu@intel.com>
Signed-off-by: Jacob Pan <jacob.jun.pan@linux.intel.com>
---
 drivers/iommu/iommu.c | 22 ++++++++++++++++++++++
 include/linux/iommu.h |  6 ++++++
 2 files changed, 28 insertions(+)

diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index 7dd51c5d2ba1..9e5de9abebdf 100644
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -1696,6 +1696,28 @@ int iommu_sva_unbind_gpasid(struct iommu_domain *domain, struct device *dev,
 }
 EXPORT_SYMBOL_GPL(iommu_sva_unbind_gpasid);
 
+
+/**
+ * Maintain a UAPI version to user data structure size lookup for each
+ * API function types we support. e.g. bind guest pasid, cache invalidation.
+ * As data structures being extended with new members, the offsetofend()
+ * will identify the new sizes.
+ */
+const static int iommu_uapi_data_size[NR_IOMMU_UAPI_TYPE][IOMMU_UAPI_VERSION] = {
+	/* IOMMU_UAPI_BIND_GPASID */
+	{offsetofend(struct iommu_gpasid_bind_data, vtd)},
+	/* IOMMU_UAPI_CACHE_INVAL */
+	{offsetofend(struct iommu_cache_invalidate_info, addr_info)},
+	/* IOMMU_UAPI_PAGE_RESP */
+	{offsetofend(struct iommu_page_response, code)},
+};
+
+int iommu_uapi_get_data_size(int type, int version)
+{
+	return iommu_uapi_data_size[type][version - 1];
+}
+EXPORT_SYMBOL_GPL(iommu_uapi_get_data_size);
+
 static void __iommu_detach_device(struct iommu_domain *domain,
 				  struct device *dev)
 {
diff --git a/include/linux/iommu.h b/include/linux/iommu.h
index 9718c109ea0a..416fe02160ba 100644
--- a/include/linux/iommu.h
+++ b/include/linux/iommu.h
@@ -500,6 +500,7 @@ extern int iommu_report_device_fault(struct device *dev,
 				     struct iommu_fault_event *evt);
 extern int iommu_page_response(struct device *dev,
 			       struct iommu_page_response *msg);
+extern int iommu_uapi_get_data_size(int type, int version);
 
 extern int iommu_group_id(struct iommu_group *group);
 extern struct iommu_group *iommu_group_get_for_dev(struct device *dev);
@@ -885,6 +886,11 @@ static inline int iommu_page_response(struct device *dev,
 	return -ENODEV;
 }
 
+static int iommu_uapi_get_data_size(int type, int version)
+{
+	return -ENODEV;
+}
+
 static inline int iommu_group_id(struct iommu_group *group)
 {
 	return -ENODEV;
-- 
2.7.4

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