linux-kernel - [PATCH 1/3] iommu/uapi: Define uapi version and capabilities

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Message-Id: <1580277724-66994-2-git-send-email-jacob.jun.pan@linux.intel.com>
Date:   Tue, 28 Jan 2020 22:02:02 -0800
From:   Jacob Pan <jacob.jun.pan@...ux.intel.com>
To:     iommu@...ts.linux-foundation.org,
        LKML <linux-kernel@...r.kernel.org>,
        "Lu Baolu" <baolu.lu@...ux.intel.com>,
        Joerg Roedel <joro@...tes.org>,
        David Woodhouse <dwmw2@...radead.org>
Cc:     "Yi Liu" <yi.l.liu@...el.com>,
        "Tian, Kevin" <kevin.tian@...el.com>,
        Raj Ashok <ashok.raj@...el.com>,
        Alex Williamson <alex.williamson@...hat.com>,
        "Christoph Hellwig" <hch@...radead.org>,
        Jean-Philippe Brucker <jean-philippe@...aro.com>,
        Jonathan Cameron <jic23@...nel.org>,
        Eric Auger <eric.auger@...hat.com>,
        Jacob Pan <jacob.jun.pan@...ux.intel.com>
Subject: [PATCH 1/3] iommu/uapi: Define uapi version and capabilities

Define a unified UAPI version to be used for compatibility
checks between user and kernel.

Signed-off-by: Liu Yi L <yi.l.liu@...el.com>
Signed-off-by: Jacob Pan <jacob.jun.pan@...ux.intel.com>
---
 include/uapi/linux/iommu.h | 48 ++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 48 insertions(+)

diff --git a/include/uapi/linux/iommu.h b/include/uapi/linux/iommu.h
index fcafb6401430..65a26c2519ee 100644
--- a/include/uapi/linux/iommu.h
+++ b/include/uapi/linux/iommu.h
@@ -8,6 +8,54 @@
 
 #include <linux/types.h>
 
+/**
+ * Current version of the IOMMU user API. This is intended for query
+ * between user and kernel to determine compatible data structures.
+ *
+ * Having a single UAPI version to govern the user-kernel data structures
+ * makes compatibility check straightforward. On the contrary, supporting
+ * combinations of multiple versions of the data can be a nightmare.
+ *
+ * UAPI version can be bumped up with the following rules:
+ * 1. All data structures passed between user and kernel space share
+ *    the same version number. i.e. any extension to to any structure
+ *    results in version bump up.
+ *
+ * 2. Data structures are open to extension but closed to modification.
+ *    New fields must be added at the end of each data structure with
+ *    64bit alignment. Flag bits can be added without size change but
+ *    existing ones cannot be altered.
+ *
+ * 3. Versions are backward compatible.
+ *
+ * 4. Version to size lookup is supported by kernel internal API for each
+ *    API function type. @version is mandatory for new data structures
+ *    and must be at the beginning with type of __u32.
+ */
+#define IOMMU_UAPI_VERSION	1
+static inline int iommu_get_uapi_version(void)
+{
+	return IOMMU_UAPI_VERSION;
+}
+
+/*
+ * Supported UAPI features that can be reported to user space.
+ * These types represent the capability available in the kernel.
+ *
+ * REVISIT: UAPI version also implies the capabilities. Should we
+ * report them explicitly?
+ */
+enum IOMMU_UAPI_DATA_TYPES {
+	IOMMU_UAPI_BIND_GPASID,
+	IOMMU_UAPI_CACHE_INVAL,
+	IOMMU_UAPI_PAGE_RESP,
+	NR_IOMMU_UAPI_TYPE,
+};
+
+#define IOMMU_UAPI_CAP_MASK ((1 << IOMMU_UAPI_BIND_GPASID) |	\
+				(1 << IOMMU_UAPI_CACHE_INVAL) |	\
+				(1 << IOMMU_UAPI_PAGE_RESP))
+
 #define IOMMU_FAULT_PERM_READ	(1 << 0) /* read */
 #define IOMMU_FAULT_PERM_WRITE	(1 << 1) /* write */
 #define IOMMU_FAULT_PERM_EXEC	(1 << 2) /* exec */
-- 
2.7.4