[PATCH v4 2/5] iommu/uapi: Add argsz for user filled data

[Jacob Pan]

As IOMMU UAPI gets extended, user data size may increase. To support
backward compatibiliy, this patch introduces a size field to each UAPI
data structures. It is *always* the responsibility for the user to fill in
the correct size.

Specific scenarios for user data handling are documented in:
Documentation/userspace-api/iommu.rst

Signed-off-by: Liu Yi L <yi.l.liu@xxxxxxxxx>
Signed-off-by: Jacob Pan <jacob.jun.pan@xxxxxxxxxxxxxxx>
---
 include/uapi/linux/iommu.h | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/include/uapi/linux/iommu.h b/include/uapi/linux/iommu.h
index e907b7091a46..303f148a5cd7 100644
--- a/include/uapi/linux/iommu.h
+++ b/include/uapi/linux/iommu.h
@@ -135,6 +135,7 @@ enum iommu_page_response_code {
 
 /**
  * struct iommu_page_response - Generic page response information
+ * @argsz: User filled size of this data
  * @version: API version of this structure
  * @flags: encodes whether the corresponding fields are valid
  *         (IOMMU_FAULT_PAGE_RESPONSE_* values)
@@ -143,6 +144,7 @@ enum iommu_page_response_code {
  * @code: response code from &enum iommu_page_response_code
  */
 struct iommu_page_response {
+	__u32	argsz;
 #define IOMMU_PAGE_RESP_VERSION_1	1
 	__u32	version;
 #define IOMMU_PAGE_RESP_PASID_VALID	(1 << 0)
@@ -218,6 +220,7 @@ struct iommu_inv_pasid_info {
 /**
  * struct iommu_cache_invalidate_info - First level/stage invalidation
  *     information
+ * @argsz: User filled size of this data
  * @version: API version of this structure
  * @cache: bitfield that allows to select which caches to invalidate
  * @granularity: defines the lowest granularity used for the invalidation:
@@ -246,6 +249,7 @@ struct iommu_inv_pasid_info {
  * must support the used granularity.
  */
 struct iommu_cache_invalidate_info {
+	__u32	argsz;
 #define IOMMU_CACHE_INVALIDATE_INFO_VERSION_1 1
 	__u32	version;
 /* IOMMU paging structure cache */
@@ -292,6 +296,7 @@ struct iommu_gpasid_bind_data_vtd {
 
 /**
  * struct iommu_gpasid_bind_data - Information about device and guest PASID binding
+ * @argsz:	User filled size of this data
  * @version:	Version of this data structure
  * @format:	PASID table entry format
  * @flags:	Additional information on guest bind request
@@ -309,6 +314,7 @@ struct iommu_gpasid_bind_data_vtd {
  * PASID to host PASID based on this bind data.
  */
 struct iommu_gpasid_bind_data {
+	__u32 argsz;
 #define IOMMU_GPASID_BIND_VERSION_1	1
 	__u32 version;
 #define IOMMU_PASID_FORMAT_INTEL_VTD	1
-- 
2.7.4