From: Jacob Pan <jacob.jun.pan@linux.intel.com>
To: Joerg Roedel <joro@8bytes.org>,
Alex Williamson <alex.williamson@redhat.com>,
"Lu Baolu" <baolu.lu@linux.intel.com>,
iommu@lists.linux-foundation.org,
LKML <linux-kernel@vger.kernel.org>,
David Woodhouse <dwmw2@infradead.org>,
Jean-Philippe Brucker <jean-philippe@linaro.com>
Cc: "Tian, Kevin" <kevin.tian@intel.com>, Raj Ashok <ashok.raj@intel.com>
Subject: [PATCH v2 1/3] iommu/uapi: Define uapi version and capabilities
Date: Wed, 25 Mar 2020 16:17:05 -0700 [thread overview]
Message-ID: <1585178227-17061-2-git-send-email-jacob.jun.pan@linux.intel.com> (raw)
In-Reply-To: <1585178227-17061-1-git-send-email-jacob.jun.pan@linux.intel.com>
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 to
maintain.
This patch defines a unified UAPI version to be used for compatibility
checks between user and kernel.
---
v2: Rewrite extension rules to disallow adding new members. Use padding
and union extensions only.
---
Signed-off-by: Liu Yi L <yi.l.liu@intel.com>
Signed-off-by: Jacob Pan <jacob.jun.pan@linux.intel.com>
Link: https://lkml.org/lkml/2020/2/3/1126
---
include/uapi/linux/iommu.h | 53 ++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 53 insertions(+)
diff --git a/include/uapi/linux/iommu.h b/include/uapi/linux/iommu.h
index d7bcbc5f79b0..25dba9198d7f 100644
--- a/include/uapi/linux/iommu.h
+++ b/include/uapi/linux/iommu.h
@@ -8,6 +8,59 @@
#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.
+ *
+ * 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 any structure
+ * results in version number increment.
+ *
+ * 2. Data structures are open to extension but closed to modification.
+ * Extensions are allowed in two places:
+ * - the padding bytes with a flag bit for each new member
+ * - new union members at the end of each structure
+ *
+ * No new members can be added after padding bytes are exhausted.
+ * The reason is that the union size can change when new members are
+ * added, having new member at the end would break backward
+ * compatibility. Expansion of the union would move the new member
+ * to different offset between versions.
+ *
+ * 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
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next prev parent reply other threads:[~2020-03-25 23:11 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-25 23:17 [PATCH v2 0/3] IOMMU user API enhancement Jacob Pan
2020-03-25 23:17 ` Jacob Pan [this message]
2020-03-26 9:23 ` [PATCH v2 1/3] iommu/uapi: Define uapi version and capabilities Christoph Hellwig
2020-03-26 16:44 ` Jacob Pan
2020-03-27 2:49 ` Tian, Kevin
2020-03-27 7:47 ` Christoph Hellwig
2020-03-27 23:53 ` Jacob Pan
2020-03-30 5:40 ` Tian, Kevin
2020-03-30 16:07 ` Jacob Pan
2020-03-31 6:06 ` Tian, Kevin
2020-03-31 15:54 ` Jacob Pan
2020-04-01 5:32 ` Tian, Kevin
2020-04-02 18:36 ` Jacob Pan
2020-04-13 20:41 ` Jacob Pan
2020-04-13 22:21 ` Alex Williamson
2020-04-14 5:05 ` Jacob Pan
2020-04-14 16:13 ` Alex Williamson
2020-04-14 17:13 ` Jacob Pan
2020-04-14 22:32 ` Jacob Pan
2020-04-14 23:47 ` Tian, Kevin
2020-04-15 15:38 ` Jacob Pan
2020-04-16 1:27 ` Tian, Kevin
2020-04-14 8:15 ` Christoph Hellwig
2020-04-14 8:11 ` Christoph Hellwig
2020-04-14 16:06 ` Jacob Pan
2020-03-25 23:17 ` [PATCH v2 2/3] iommu/uapi: Use unified UAPI version Jacob Pan
2020-03-25 23:17 ` [PATCH v2 3/3] iommu/uapi: Add helper function for size lookup Jacob Pan
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