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Subject[PATCH v2 3/3] iommu/uapi: Add helper function for size lookup
Date
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.

---
v2: Clarify size lookup array extension rules, backfill -EINVAL
if new version introduce new union members.
---

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 | 72 +++++++++++++++++++++++++++++++++++++++++++++++++++
include/linux/iommu.h | 6 +++++
2 files changed, 78 insertions(+)

diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index c476b58e0ffb..e91ced212653 100644
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -1724,6 +1724,78 @@ 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, offsetofend() is
+ * used to identify the size. In case of adding a new member to a union,
+ * offsetofend() applies to the largest member which may not be the newest.
+ *
+ * When new types are introduced with new versions, the new types for older
+ * version must be filled with -EINVAL.
+ *
+ * The table below documents UAPI revision history with the name of the
+ * newest member of each data structure. The largest member of a union was
+ * used for the initial version of each type.
+ *
+ * +--------------+---------------+
+ * | Type / | V1 |
+ * | UAPI Version | |
+ * +==============+===============+
+ * | BIND_GPASID | vtd |
+ * +--------------+---------------+
+ * | CACHE_INVAL | addr_info |
+ * +--------------+---------------+
+ * | PAGE_RESP | code |
+ * +--------------+---------------+
+ *
+ * Examples of future extensions:
+ * V2 addes new member to the union
+ * +--------------+---------------+---------------+
+ * | Type / | V1 | V2 |
+ * | UAPI Version | | |
+ * +==============+===============+===============+
+ * | BIND_GPASID | vtd | smmu_v3 |
+ * +--------------+---------------+---------------+
+ * | CACHE_INVAL | addr_info | new_info |
+ * +--------------+---------------+---------------+
+ * | PAGE_RESP | code | N/A |
+ * +--------------+---------------+---------------+
+ *
+ * V3 introduces a new UAPI data type: NEW_TYPE but with no new members
+ * added to the existing types.
+ * +--------------+---------------+---------------+---------------+
+ * | Type / | V1 | V2 | V3 |
+ * | UAPI Version | | | |
+ * +==============+===============+===============+===============+
+ * | BIND_GPASID | vtd | smmu_v3 | N/A |
+ * +--------------+---------------+---------------+---------------+
+ * | CACHE_INVAL | addr_info | new_info | N/A |
+ * +--------------+---------------+---------------+---------------+
+ * | PAGE_RESP | code | N/A | N/A |
+ * +--------------+---------------+---------------+---------------+
+ * | NEW_TYPE | -EINVAL | -EINVAL | largest_member|
+ * +--------------+---------------+---------------+---------------+
+ */
+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)
+{
+ if (type >= NR_IOMMU_UAPI_TYPE || version > IOMMU_UAPI_VERSION)
+ return -EINVAL;
+
+ 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 d1b5f4d98569..4908919a98f1 100644
--- a/include/linux/iommu.h
+++ b/include/linux/iommu.h
@@ -510,6 +510,7 @@ 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);
@@ -897,6 +898,11 @@ static inline int iommu_page_response(struct device *dev,
return -ENODEV;
}

+static inline 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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