IOMMU Archive on lore.kernel.org
 help / color / Atom feed
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
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

_______________________________________________
iommu mailing list
iommu@lists.linux-foundation.org
https://lists.linuxfoundation.org/mailman/listinfo/iommu

  reply index

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

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=1585178227-17061-2-git-send-email-jacob.jun.pan@linux.intel.com \
    --to=jacob.jun.pan@linux.intel.com \
    --cc=alex.williamson@redhat.com \
    --cc=ashok.raj@intel.com \
    --cc=baolu.lu@linux.intel.com \
    --cc=dwmw2@infradead.org \
    --cc=iommu@lists.linux-foundation.org \
    --cc=jean-philippe@linaro.com \
    --cc=joro@8bytes.org \
    --cc=kevin.tian@intel.com \
    --cc=linux-kernel@vger.kernel.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

IOMMU Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/linux-iommu/0 linux-iommu/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 linux-iommu linux-iommu/ https://lore.kernel.org/linux-iommu \
		iommu@lists.linux-foundation.org
	public-inbox-index linux-iommu

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.linux-foundation.lists.iommu


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git