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* [PATCH v9 0/7] IOMMU user API enhancement
@ 2020-09-11 21:57 Jacob Pan
  2020-09-11 21:57 ` [PATCH v9 1/7] docs: IOMMU user API Jacob Pan
                   ` (7 more replies)
  0 siblings, 8 replies; 17+ messages in thread
From: Jacob Pan @ 2020-09-11 21:57 UTC (permalink / raw)
  To: iommu, LKML, Joerg Roedel, Alex Williamson, Lu Baolu,
	David Woodhouse, Jonathan Corbet
  Cc: Tian, Kevin, Raj Ashok, Yi Sun, Jean-Philippe Brucker, Wu Hao

IOMMU user API header was introduced to support nested DMA translation and
related fault handling. The current UAPI data structures consist of three
areas that cover the interactions between host kernel and guest:
 - fault handling
 - cache invalidation
 - bind guest page tables, i.e. guest PASID

Future extensions are likely to support more architectures and vIOMMU features.

In the previous discussion, using user-filled data size and feature flags is
made a preferred approach over a unified version number.
https://lkml.org/lkml/2020/1/29/45

In addition to introduce argsz field to data structures, this patchset is also
trying to document the UAPI design, usage, and extension rules. VT-d driver
changes to utilize the new argsz field is included, VFIO usage is to follow.

This set is available at:
https://github.com/jacobpan/linux.git vsva_v5.9_uapi_v9

Thanks,

Jacob


Changelog:
v9
	- Directly pass PASID value to iommu_sva_unbind_gpasid() without
	  the superfluous data in struct iommu_gpasid_bind_data.
v8
	- Rebased to v5.9-rc2
	- Addressed review comments from Eric Auger
	  1. added a check for the unused vendor flags
	  2. commit message improvements
v7
	- Added PASID data format enum for range checking
	- Tidy up based on reviews from Alex W.
	- Removed doc section for vIOMMU fault handling
v6
	- Renamed all UAPI functions with iommu_uapi_ prefix
	- Replaced argsz maxsz checking with flag specific size checks
	- Documentation improvements based on suggestions by Eric Auger
	  Replaced example code with a pointer to the actual code
	- Added more checks for illegal flags combinations
	- Added doc file to MAINTAINERS
v5
	- Addjusted paddings in UAPI data to be 8 byte aligned
	- Do not clobber argsz in IOMMU core before passing on to vendor driver
	- Removed pr_warn_ for invalid UAPI data check, just return -EINVAL
	- Clarified VFIO responsibility in UAPI data handling
	- Use iommu_uapi prefix to differentiate APIs has in-kernel caller
	- Added comment for unchecked flags of invalidation granularity
	- Added example in doc to show vendor data checking

v4
	- Added checks of UAPI data for reserved fields, version, and flags.
	- Removed version check from vendor driver (vt-d)
	- Relaxed argsz check to match the UAPI struct size instead of variable
	  union size
	- Updated documentation

v3:
	- Rewrote backward compatibility rule to support existing code
	  re-compiled with newer kernel UAPI header that runs on older
	  kernel. Based on review comment from Alex W.
	  https://lore.kernel.org/linux-iommu/20200611094741.6d118fa8@w520.home/
	- Take user pointer directly in UAPI functions. Perform argsz check
	  and copy_from_user() in IOMMU driver. Eliminate the need for
	  VFIO or other upper layer to parse IOMMU data.
	- Create wrapper function for in-kernel users of UAPI functions
v2:
	- Removed unified API version and helper
	- Introduced argsz for each UAPI data
	- Introduced UAPI doc


Jacob Pan (7):
  docs: IOMMU user API
  iommu/uapi: Add argsz for user filled data
  iommu/uapi: Introduce enum type for PASID data format
  iommu/uapi: Use named union for user data
  iommu/uapi: Rename uapi functions
  iommu/uapi: Handle data and argsz filled by users
  iommu/vt-d: Check UAPI data processed by IOMMU core

 Documentation/userspace-api/iommu.rst | 211 ++++++++++++++++++++++++++++++++++
 MAINTAINERS                           |   1 +
 drivers/iommu/intel/iommu.c           |  25 ++--
 drivers/iommu/intel/svm.c             |  13 ++-
 drivers/iommu/iommu.c                 | 201 ++++++++++++++++++++++++++++++--
 include/linux/iommu.h                 |  35 ++++--
 include/uapi/linux/iommu.h            |  25 ++--
 7 files changed, 468 insertions(+), 43 deletions(-)
 create mode 100644 Documentation/userspace-api/iommu.rst

-- 
2.7.4

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

^ permalink raw reply	[flat|nested] 17+ messages in thread

* [PATCH v9 1/7] docs: IOMMU user API
  2020-09-11 21:57 [PATCH v9 0/7] IOMMU user API enhancement Jacob Pan
@ 2020-09-11 21:57 ` Jacob Pan
  2020-09-16 18:26   ` Randy Dunlap
  2020-09-11 21:57 ` [PATCH v9 2/7] iommu/uapi: Add argsz for user filled data Jacob Pan
                   ` (6 subsequent siblings)
  7 siblings, 1 reply; 17+ messages in thread
From: Jacob Pan @ 2020-09-11 21:57 UTC (permalink / raw)
  To: iommu, LKML, Joerg Roedel, Alex Williamson, Lu Baolu,
	David Woodhouse, Jonathan Corbet
  Cc: Tian, Kevin, Raj Ashok, Yi Sun, Jean-Philippe Brucker, Wu Hao

IOMMU UAPI is newly introduced to support communications between guest
virtual IOMMU and host IOMMU. There has been lots of discussions on how
it should work with VFIO UAPI and userspace in general.

This document is intended to clarify the UAPI design and usage. The
mechanics of how future extensions should be achieved are also covered
in this documentation.

Reviewed-by: Eric Auger <eric.auger@redhat.com>
Signed-off-by: Liu Yi L <yi.l.liu@intel.com>
Signed-off-by: Jacob Pan <jacob.jun.pan@linux.intel.com>
---
 Documentation/userspace-api/iommu.rst | 211 ++++++++++++++++++++++++++++++++++
 MAINTAINERS                           |   1 +
 2 files changed, 212 insertions(+)
 create mode 100644 Documentation/userspace-api/iommu.rst

diff --git a/Documentation/userspace-api/iommu.rst b/Documentation/userspace-api/iommu.rst
new file mode 100644
index 000000000000..1e68e8f05bb3
--- /dev/null
+++ b/Documentation/userspace-api/iommu.rst
@@ -0,0 +1,211 @@
+.. SPDX-License-Identifier: GPL-2.0
+.. iommu:
+
+=====================================
+IOMMU Userspace API
+=====================================
+
+IOMMU UAPI is used for virtualization cases where communications are
+needed between physical and virtual IOMMU drivers. For baremetal
+usage, the IOMMU is a system device which does not need to communicate
+with user space directly.
+
+The primary use cases are guest Shared Virtual Address (SVA) and
+guest IO virtual address (IOVA), wherin the vIOMMU implementation
+relies on the physical IOMMU and for this reason requires interactions
+with the host driver.
+
+.. contents:: :local:
+
+Functionalities
+===============
+Communications of user and kernel involve both directions. The
+supported user-kernel APIs are as follows:
+
+1. Alloc/Free PASID
+2. Bind/Unbind guest PASID (e.g. Intel VT-d)
+3. Bind/Unbind guest PASID table (e.g. ARM SMMU)
+4. Invalidate IOMMU caches upon guest requests
+5. Report errors to the guest and serve page requests
+
+Requirements
+============
+The IOMMU UAPIs are generic and extensible to meet the following
+requirements:
+
+1. Emulated and para-virtualised vIOMMUs
+2. Multiple vendors (Intel VT-d, ARM SMMU, etc.)
+3. Extensions to the UAPI shall not break existing user space
+
+Interfaces
+==========
+Although the data structures defined in IOMMU UAPI are self-contained,
+there is no user API functions introduced. Instead, IOMMU UAPI is
+designed to work with existing user driver frameworks such as VFIO.
+
+Extension Rules & Precautions
+-----------------------------
+When IOMMU UAPI gets extended, the data structures can *only* be
+modified in two ways:
+
+1. Adding new fields by re-purposing the padding[] field. No size change.
+2. Adding new union members at the end. May increase the structure sizes.
+
+No new fields can be added *after* the variable sized union in that it
+will break backward compatibility when offset moves. A new flag must
+be introduced whenever a change affects the structure using either
+method. The IOMMU driver processes the data based on flags which
+ensures backward compatibility.
+
+Version field is only reserved for the unlikely event of UAPI upgrade
+at its entirety.
+
+It's *always* the caller's responsibility to indicate the size of the
+structure passed by setting argsz appropriately.
+Though at the same time, argsz is user provided data which is not
+trusted. The argsz field allows the user app to indicate how much data
+it is providing, it's still the kernel's responsibility to validate
+whether it's correct and sufficient for the requested operation.
+
+Compatibility Checking
+----------------------
+When IOMMU UAPI extension results in some structure size increase,
+IOMMU UAPI code shall handle the following cases:
+
+1. User and kernel has exact size match
+2. An older user with older kernel header (smaller UAPI size) running on a
+   newer kernel (larger UAPI size)
+3. A newer user with newer kernel header (larger UAPI size) running
+   on an older kernel.
+4. A malicious/misbehaving user pass illegal/invalid size but within
+   range. The data may contain garbage.
+
+Feature Checking
+----------------
+While launching a guest with vIOMMU, it is strongly advised to check
+the compatibility upfront, as some subsequent errors happening during
+vIOMMU operation, such as cache invalidation failures cannot be nicely
+escaladated to the guest due to IOMMU specifications. This can lead to
+catastrophic failures for the users.
+
+User applications such as QEMU are expected to import kernel UAPI
+headers. Backward compatibility is supported per feature flags.
+For example, an older QEMU (with older kernel header) can run on newer
+kernel. Newer QEMU (with new kernel header) may refuse to initialize
+on an older kernel if new feature flags are not supported by older
+kernel. Simply recompiling existing code with newer kernel header should
+not be an issue in that only existing flags are used.
+
+IOMMU vendor driver should report the below features to IOMMU UAPI
+consumers (e.g. via VFIO).
+
+1. IOMMU_NESTING_FEAT_SYSWIDE_PASID
+2. IOMMU_NESTING_FEAT_BIND_PGTBL
+3. IOMMU_NESTING_FEAT_BIND_PASID_TABLE
+4. IOMMU_NESTING_FEAT_CACHE_INVLD
+5. IOMMU_NESTING_FEAT_PAGE_REQUEST
+
+Take VFIO as example, upon request from VFIO user space (e.g. QEMU),
+VFIO kernel code shall query IOMMU vendor driver for the support of
+the above features. Query result can then be reported back to the
+user-space caller. Details can be found in
+Documentation/driver-api/vfio.rst.
+
+
+Data Passing Example with VFIO
+------------------------------
+As the ubiquitous userspace driver framework, VFIO is already IOMMU
+aware and shares many key concepts such as device model, group, and
+protection domain. Other user driver frameworks can also be extended
+to support IOMMU UAPI but it is outside the scope of this document.
+
+In this tight-knit VFIO-IOMMU interface, the ultimate consumer of the
+IOMMU UAPI data is the host IOMMU driver. VFIO facilitates user-kernel
+transport, capability checking, security, and life cycle management of
+process address space ID (PASID).
+
+VFIO layer conveys the data structures down to the IOMMU driver, it
+follows the pattern below::
+
+   struct {
+	__u32 argsz;
+	__u32 flags;
+	__u8  data[];
+   };
+
+Here data[] contains the IOMMU UAPI data structures. VFIO has the
+freedom to bundle the data as well as parse data size based on its own flags.
+
+In order to determine the size and feature set of the user data, argsz
+and flags (or the equivalent) are also embedded in the IOMMU UAPI data
+structures.
+
+A "__u32 argsz" field is *always* at the beginning of each structure.
+
+For example:
+::
+
+   struct iommu_cache_invalidate_info {
+	__u32	argsz;
+	#define IOMMU_CACHE_INVALIDATE_INFO_VERSION_1 1
+	__u32	version;
+	/* IOMMU paging structure cache */
+	#define IOMMU_CACHE_INV_TYPE_IOTLB	(1 << 0) /* IOMMU IOTLB */
+	#define IOMMU_CACHE_INV_TYPE_DEV_IOTLB	(1 << 1) /* Device IOTLB */
+	#define IOMMU_CACHE_INV_TYPE_PASID	(1 << 2) /* PASID cache */
+	#define IOMMU_CACHE_INV_TYPE_NR		(3)
+	__u8	cache;
+	__u8	granularity;
+	__u8	padding[6];
+	union {
+		struct iommu_inv_pasid_info pasid_info;
+		struct iommu_inv_addr_info addr_info;
+	} granu;
+   };
+
+VFIO is responsible for checking its own argsz and flags. It then
+invokes appropriate IOMMU UAPI functions. The user pointers are passed
+to the IOMMU layer for further processing. The responsibilities are
+divided as follows:
+
+- Generic IOMMU layer checks argsz range based on UAPI data in the
+  current kernel version
+
+- Generic IOMMU layer checks content of the UAPI data for non-zero
+  reserved bits in flags, padding fields, and unsupported version.
+  This is to ensure not breaking userspace in the future when these
+  fields or flags are used.
+
+- Vendor IOMMU driver checks argsz based on vendor flags, UAPI data
+  is consumed based on flags. Vendor driver has access to
+  unadulterated argsz value in case of vendor specific future
+  extensions. Currently, it does not perform the copy_from_user()
+  itself. A __user pointer can be provided in some future scenarios
+  where there's vendor data outside of the structure definition.
+
+IOMMU code treats UAPI data into two categories:
+
+- structure contains vendor data
+  (Example: iommu_uapi_cache_invalidate())
+
+- structure contains only generic data
+  (Example: iommu_uapi_sva_bind_gpasid())
+
+
+
+Sharing UAPI with in-kernel users
+---------------------------------
+For UAPIs that are shared with in-kernel users, a wrapper function is
+provided to distinguish the callers. For example,
+
+Userspace caller ::
+
+  int iommu_uapi_sva_unbind_gpasid(struct iommu_domain *domain,
+                                   struct device *dev,
+                                   void __user *udata)
+
+In-kernel caller ::
+
+  int iommu_sva_unbind_gpasid(struct iommu_domain *domain,
+                                   struct device *dev,
+                                   struct iommu_gpasid_bind_data *data)
diff --git a/MAINTAINERS b/MAINTAINERS
index b5cfab015bd6..68e6aba2afba 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -9117,6 +9117,7 @@ L:	iommu@lists.linux-foundation.org
 S:	Maintained
 T:	git git://git.kernel.org/pub/scm/linux/kernel/git/joro/iommu.git
 F:	Documentation/devicetree/bindings/iommu/
+F:	Documentation/userspace-api/iommu.rst
 F:	drivers/iommu/
 F:	include/linux/iommu.h
 F:	include/linux/iova.h
-- 
2.7.4

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

^ permalink raw reply	[flat|nested] 17+ messages in thread

* [PATCH v9 2/7] iommu/uapi: Add argsz for user filled data
  2020-09-11 21:57 [PATCH v9 0/7] IOMMU user API enhancement Jacob Pan
  2020-09-11 21:57 ` [PATCH v9 1/7] docs: IOMMU user API Jacob Pan
@ 2020-09-11 21:57 ` Jacob Pan
  2020-09-11 21:57 ` [PATCH v9 3/7] iommu/uapi: Introduce enum type for PASID data format Jacob Pan
                   ` (5 subsequent siblings)
  7 siblings, 0 replies; 17+ messages in thread
From: Jacob Pan @ 2020-09-11 21:57 UTC (permalink / raw)
  To: iommu, LKML, Joerg Roedel, Alex Williamson, Lu Baolu,
	David Woodhouse, Jonathan Corbet
  Cc: Tian, Kevin, Raj Ashok, Yi Sun, Jean-Philippe Brucker, Wu Hao

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. Padding fields are adjusted to ensure 8 byte alignment.

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

As there is no current users of the API, struct version is not
incremented.

Reviewed-by: Eric Auger <eric.auger@redhat.com>
Signed-off-by: Liu Yi L <yi.l.liu@intel.com>
Signed-off-by: Jacob Pan <jacob.jun.pan@linux.intel.com>
---
 include/uapi/linux/iommu.h | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/include/uapi/linux/iommu.h b/include/uapi/linux/iommu.h
index c2b2caf9ed41..b42acc8fe007 100644
--- a/include/uapi/linux/iommu.h
+++ b/include/uapi/linux/iommu.h
@@ -139,6 +139,7 @@ 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)
@@ -147,6 +148,7 @@ 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)
@@ -222,6 +224,7 @@ 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:
@@ -250,6 +253,7 @@ 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 */
@@ -259,7 +263,7 @@ struct iommu_cache_invalidate_info {
 #define IOMMU_CACHE_INV_TYPE_NR		(3)
 	__u8	cache;
 	__u8	granularity;
-	__u8	padding[2];
+	__u8	padding[6];
 	union {
 		struct iommu_inv_pasid_info pasid_info;
 		struct iommu_inv_addr_info addr_info;
@@ -296,6 +300,7 @@ 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
@@ -313,17 +318,18 @@ 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
 	__u32 format;
+	__u32 addr_width;
 #define IOMMU_SVA_GPASID_VAL	(1 << 0) /* guest PASID valid */
 	__u64 flags;
 	__u64 gpgd;
 	__u64 hpasid;
 	__u64 gpasid;
-	__u32 addr_width;
-	__u8  padding[12];
+	__u8  padding[8];
 	/* Vendor specific data */
 	union {
 		struct iommu_gpasid_bind_data_vtd vtd;
-- 
2.7.4

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

^ permalink raw reply	[flat|nested] 17+ messages in thread

* [PATCH v9 3/7] iommu/uapi: Introduce enum type for PASID data format
  2020-09-11 21:57 [PATCH v9 0/7] IOMMU user API enhancement Jacob Pan
  2020-09-11 21:57 ` [PATCH v9 1/7] docs: IOMMU user API Jacob Pan
  2020-09-11 21:57 ` [PATCH v9 2/7] iommu/uapi: Add argsz for user filled data Jacob Pan
@ 2020-09-11 21:57 ` Jacob Pan
  2020-09-18  9:44   ` Joerg Roedel
  2020-09-11 21:57 ` [PATCH v9 4/7] iommu/uapi: Use named union for user data Jacob Pan
                   ` (4 subsequent siblings)
  7 siblings, 1 reply; 17+ messages in thread
From: Jacob Pan @ 2020-09-11 21:57 UTC (permalink / raw)
  To: iommu, LKML, Joerg Roedel, Alex Williamson, Lu Baolu,
	David Woodhouse, Jonathan Corbet
  Cc: Tian, Kevin, Raj Ashok, Yi Sun, Jean-Philippe Brucker, Wu Hao

There can be multiple vendor-specific PASID data formats used in UAPI
structures. This patch adds enum type with a last entry which makes
range checking much easier.

Suggested-by: Alex Williamson <alex.williamson@redhat.com>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Signed-off-by: Jacob Pan <jacob.jun.pan@linux.intel.com>
---
 include/uapi/linux/iommu.h | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/include/uapi/linux/iommu.h b/include/uapi/linux/iommu.h
index b42acc8fe007..7cc6ee6c41f7 100644
--- a/include/uapi/linux/iommu.h
+++ b/include/uapi/linux/iommu.h
@@ -298,11 +298,16 @@ struct iommu_gpasid_bind_data_vtd {
 					 IOMMU_SVA_VTD_GPASID_PCD |  \
 					 IOMMU_SVA_VTD_GPASID_PWT)
 
+enum iommu_pasid_data_format {
+	IOMMU_PASID_FORMAT_INTEL_VTD = 1,
+	IOMMU_PASID_FORMAT_LAST,
+};
+
 /**
  * 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
+ * @format:	PASID table entry format of enum iommu_pasid_data_format type
  * @flags:	Additional information on guest bind request
  * @gpgd:	Guest page directory base of the guest mm to bind
  * @hpasid:	Process address space ID used for the guest mm in host IOMMU
@@ -321,7 +326,6 @@ struct iommu_gpasid_bind_data {
 	__u32 argsz;
 #define IOMMU_GPASID_BIND_VERSION_1	1
 	__u32 version;
-#define IOMMU_PASID_FORMAT_INTEL_VTD	1
 	__u32 format;
 	__u32 addr_width;
 #define IOMMU_SVA_GPASID_VAL	(1 << 0) /* guest PASID valid */
-- 
2.7.4

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

^ permalink raw reply	[flat|nested] 17+ messages in thread

* [PATCH v9 4/7] iommu/uapi: Use named union for user data
  2020-09-11 21:57 [PATCH v9 0/7] IOMMU user API enhancement Jacob Pan
                   ` (2 preceding siblings ...)
  2020-09-11 21:57 ` [PATCH v9 3/7] iommu/uapi: Introduce enum type for PASID data format Jacob Pan
@ 2020-09-11 21:57 ` Jacob Pan
  2020-09-11 21:57 ` [PATCH v9 5/7] iommu/uapi: Rename uapi functions Jacob Pan
                   ` (3 subsequent siblings)
  7 siblings, 0 replies; 17+ messages in thread
From: Jacob Pan @ 2020-09-11 21:57 UTC (permalink / raw)
  To: iommu, LKML, Joerg Roedel, Alex Williamson, Lu Baolu,
	David Woodhouse, Jonathan Corbet
  Cc: Tian, Kevin, Raj Ashok, Yi Sun, Jean-Philippe Brucker, Wu Hao

IOMMU UAPI data size is filled by the user space which must be validated
by the kernel. To ensure backward compatibility, user data can only be
extended by either re-purpose padding bytes or extend the variable sized
union at the end. No size change is allowed before the union. Therefore,
the minimum size is the offset of the union.

To use offsetof() on the union, we must make it named.

Link: https://lore.kernel.org/linux-iommu/20200611145518.0c2817d6@x1.home/
Signed-off-by: Jacob Pan <jacob.jun.pan@linux.intel.com>
Reviewed-by: Lu Baolu <baolu.lu@linux.intel.com>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
---
 drivers/iommu/intel/iommu.c | 22 +++++++++++-----------
 drivers/iommu/intel/svm.c   |  2 +-
 include/uapi/linux/iommu.h  |  4 ++--
 3 files changed, 14 insertions(+), 14 deletions(-)

diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
index 87b17bac04c2..461f3a6864d4 100644
--- a/drivers/iommu/intel/iommu.c
+++ b/drivers/iommu/intel/iommu.c
@@ -5434,8 +5434,8 @@ intel_iommu_sva_invalidate(struct iommu_domain *domain, struct device *dev,
 
 	/* Size is only valid in address selective invalidation */
 	if (inv_info->granularity == IOMMU_INV_GRANU_ADDR)
-		size = to_vtd_size(inv_info->addr_info.granule_size,
-				   inv_info->addr_info.nb_granules);
+		size = to_vtd_size(inv_info->granu.addr_info.granule_size,
+				   inv_info->granu.addr_info.nb_granules);
 
 	for_each_set_bit(cache_type,
 			 (unsigned long *)&inv_info->cache,
@@ -5456,20 +5456,20 @@ intel_iommu_sva_invalidate(struct iommu_domain *domain, struct device *dev,
 		 * granularity.
 		 */
 		if (inv_info->granularity == IOMMU_INV_GRANU_PASID &&
-		    (inv_info->pasid_info.flags & IOMMU_INV_PASID_FLAGS_PASID))
-			pasid = inv_info->pasid_info.pasid;
+		    (inv_info->granu.pasid_info.flags & IOMMU_INV_PASID_FLAGS_PASID))
+			pasid = inv_info->granu.pasid_info.pasid;
 		else if (inv_info->granularity == IOMMU_INV_GRANU_ADDR &&
-			 (inv_info->addr_info.flags & IOMMU_INV_ADDR_FLAGS_PASID))
-			pasid = inv_info->addr_info.pasid;
+			 (inv_info->granu.addr_info.flags & IOMMU_INV_ADDR_FLAGS_PASID))
+			pasid = inv_info->granu.addr_info.pasid;
 
 		switch (BIT(cache_type)) {
 		case IOMMU_CACHE_INV_TYPE_IOTLB:
 			/* HW will ignore LSB bits based on address mask */
 			if (inv_info->granularity == IOMMU_INV_GRANU_ADDR &&
 			    size &&
-			    (inv_info->addr_info.addr & ((BIT(VTD_PAGE_SHIFT + size)) - 1))) {
+			    (inv_info->granu.addr_info.addr & ((BIT(VTD_PAGE_SHIFT + size)) - 1))) {
 				pr_err_ratelimited("User address not aligned, 0x%llx, size order %llu\n",
-						   inv_info->addr_info.addr, size);
+						   inv_info->granu.addr_info.addr, size);
 			}
 
 			/*
@@ -5477,9 +5477,9 @@ intel_iommu_sva_invalidate(struct iommu_domain *domain, struct device *dev,
 			 * We use npages = -1 to indicate that.
 			 */
 			qi_flush_piotlb(iommu, did, pasid,
-					mm_to_dma_pfn(inv_info->addr_info.addr),
+					mm_to_dma_pfn(inv_info->granu.addr_info.addr),
 					(granu == QI_GRAN_NONG_PASID) ? -1 : 1 << size,
-					inv_info->addr_info.flags & IOMMU_INV_ADDR_FLAGS_LEAF);
+					inv_info->granu.addr_info.flags & IOMMU_INV_ADDR_FLAGS_LEAF);
 
 			if (!info->ats_enabled)
 				break;
@@ -5502,7 +5502,7 @@ intel_iommu_sva_invalidate(struct iommu_domain *domain, struct device *dev,
 				size = 64 - VTD_PAGE_SHIFT;
 				addr = 0;
 			} else if (inv_info->granularity == IOMMU_INV_GRANU_ADDR) {
-				addr = inv_info->addr_info.addr;
+				addr = inv_info->granu.addr_info.addr;
 			}
 
 			if (info->ats_enabled)
diff --git a/drivers/iommu/intel/svm.c b/drivers/iommu/intel/svm.c
index 95c3164a2302..99353d6468fa 100644
--- a/drivers/iommu/intel/svm.c
+++ b/drivers/iommu/intel/svm.c
@@ -370,7 +370,7 @@ int intel_svm_bind_gpasid(struct iommu_domain *domain, struct device *dev,
 	spin_lock(&iommu->lock);
 	ret = intel_pasid_setup_nested(iommu, dev,
 				       (pgd_t *)(uintptr_t)data->gpgd,
-				       data->hpasid, &data->vtd, dmar_domain,
+				       data->hpasid, &data->vendor.vtd, dmar_domain,
 				       data->addr_width);
 	spin_unlock(&iommu->lock);
 	if (ret) {
diff --git a/include/uapi/linux/iommu.h b/include/uapi/linux/iommu.h
index 7cc6ee6c41f7..c64bca5af419 100644
--- a/include/uapi/linux/iommu.h
+++ b/include/uapi/linux/iommu.h
@@ -267,7 +267,7 @@ struct iommu_cache_invalidate_info {
 	union {
 		struct iommu_inv_pasid_info pasid_info;
 		struct iommu_inv_addr_info addr_info;
-	};
+	} granu;
 };
 
 /**
@@ -337,7 +337,7 @@ struct iommu_gpasid_bind_data {
 	/* Vendor specific data */
 	union {
 		struct iommu_gpasid_bind_data_vtd vtd;
-	};
+	} vendor;
 };
 
 #endif /* _UAPI_IOMMU_H */
-- 
2.7.4

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

^ permalink raw reply	[flat|nested] 17+ messages in thread

* [PATCH v9 5/7] iommu/uapi: Rename uapi functions
  2020-09-11 21:57 [PATCH v9 0/7] IOMMU user API enhancement Jacob Pan
                   ` (3 preceding siblings ...)
  2020-09-11 21:57 ` [PATCH v9 4/7] iommu/uapi: Use named union for user data Jacob Pan
@ 2020-09-11 21:57 ` Jacob Pan
  2020-09-11 21:57 ` [PATCH v9 6/7] iommu/uapi: Handle data and argsz filled by users Jacob Pan
                   ` (2 subsequent siblings)
  7 siblings, 0 replies; 17+ messages in thread
From: Jacob Pan @ 2020-09-11 21:57 UTC (permalink / raw)
  To: iommu, LKML, Joerg Roedel, Alex Williamson, Lu Baolu,
	David Woodhouse, Jonathan Corbet
  Cc: Tian, Kevin, Raj Ashok, Yi Sun, Jean-Philippe Brucker, Wu Hao

User APIs such as iommu_sva_unbind_gpasid() may also be used by the
kernel. Since we introduced user pointer to the UAPI functions,
in-kernel callers cannot share the same APIs. In-kernel callers are also
trusted, there is no need to validate the data.

We plan to have two flavors of the same API functions, one called
through ioctls, carrying a user pointer and one called directly with
valid IOMMU UAPI structs. To differentiate both, let's rename existing
functions with an iommu_uapi_ prefix.

Suggested-by: Alex Williamson <alex.williamson@redhat.com>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Signed-off-by: Jacob Pan <jacob.jun.pan@linux.intel.com>
---
 drivers/iommu/iommu.c | 18 +++++++++---------
 include/linux/iommu.h | 31 ++++++++++++++++---------------
 2 files changed, 25 insertions(+), 24 deletions(-)

diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index 609bd25bf154..4ae02291ccc2 100644
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -1961,35 +1961,35 @@ int iommu_attach_device(struct iommu_domain *domain, struct device *dev)
 }
 EXPORT_SYMBOL_GPL(iommu_attach_device);
 
-int iommu_cache_invalidate(struct iommu_domain *domain, struct device *dev,
-			   struct iommu_cache_invalidate_info *inv_info)
+int iommu_uapi_cache_invalidate(struct iommu_domain *domain, struct device *dev,
+				struct iommu_cache_invalidate_info *inv_info)
 {
 	if (unlikely(!domain->ops->cache_invalidate))
 		return -ENODEV;
 
 	return domain->ops->cache_invalidate(domain, dev, inv_info);
 }
-EXPORT_SYMBOL_GPL(iommu_cache_invalidate);
+EXPORT_SYMBOL_GPL(iommu_uapi_cache_invalidate);
 
-int iommu_sva_bind_gpasid(struct iommu_domain *domain,
-			   struct device *dev, struct iommu_gpasid_bind_data *data)
+int iommu_uapi_sva_bind_gpasid(struct iommu_domain *domain,
+			       struct device *dev, struct iommu_gpasid_bind_data *data)
 {
 	if (unlikely(!domain->ops->sva_bind_gpasid))
 		return -ENODEV;
 
 	return domain->ops->sva_bind_gpasid(domain, dev, data);
 }
-EXPORT_SYMBOL_GPL(iommu_sva_bind_gpasid);
+EXPORT_SYMBOL_GPL(iommu_uapi_sva_bind_gpasid);
 
-int iommu_sva_unbind_gpasid(struct iommu_domain *domain, struct device *dev,
-			     ioasid_t pasid)
+int iommu_uapi_sva_unbind_gpasid(struct iommu_domain *domain, struct device *dev,
+				 ioasid_t pasid)
 {
 	if (unlikely(!domain->ops->sva_unbind_gpasid))
 		return -ENODEV;
 
 	return domain->ops->sva_unbind_gpasid(dev, pasid);
 }
-EXPORT_SYMBOL_GPL(iommu_sva_unbind_gpasid);
+EXPORT_SYMBOL_GPL(iommu_uapi_sva_unbind_gpasid);
 
 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 fee209efb756..710d5d2691eb 100644
--- a/include/linux/iommu.h
+++ b/include/linux/iommu.h
@@ -424,13 +424,13 @@ extern int iommu_attach_device(struct iommu_domain *domain,
 			       struct device *dev);
 extern void iommu_detach_device(struct iommu_domain *domain,
 				struct device *dev);
-extern int iommu_cache_invalidate(struct iommu_domain *domain,
-				  struct device *dev,
-				  struct iommu_cache_invalidate_info *inv_info);
-extern int iommu_sva_bind_gpasid(struct iommu_domain *domain,
-		struct device *dev, struct iommu_gpasid_bind_data *data);
-extern int iommu_sva_unbind_gpasid(struct iommu_domain *domain,
-				struct device *dev, ioasid_t pasid);
+extern int iommu_uapi_cache_invalidate(struct iommu_domain *domain,
+				       struct device *dev,
+				       struct iommu_cache_invalidate_info *inv_info);
+extern int iommu_uapi_sva_bind_gpasid(struct iommu_domain *domain,
+				      struct device *dev, struct iommu_gpasid_bind_data *data);
+extern int iommu_uapi_sva_unbind_gpasid(struct iommu_domain *domain,
+					struct device *dev, ioasid_t pasid);
 extern struct iommu_domain *iommu_get_domain_for_dev(struct device *dev);
 extern struct iommu_domain *iommu_get_dma_domain(struct device *dev);
 extern int iommu_map(struct iommu_domain *domain, unsigned long iova,
@@ -1032,21 +1032,22 @@ static inline int iommu_sva_get_pasid(struct iommu_sva *handle)
 	return IOMMU_PASID_INVALID;
 }
 
-static inline int
-iommu_cache_invalidate(struct iommu_domain *domain,
-		       struct device *dev,
-		       struct iommu_cache_invalidate_info *inv_info)
+static inline int iommu_uapi_cache_invalidate(struct iommu_domain *domain,
+					      struct device *dev,
+					      struct iommu_cache_invalidate_info *inv_info)
 {
 	return -ENODEV;
 }
-static inline int iommu_sva_bind_gpasid(struct iommu_domain *domain,
-				struct device *dev, struct iommu_gpasid_bind_data *data)
+
+static inline int iommu_uapi_sva_bind_gpasid(struct iommu_domain *domain,
+					     struct device *dev,
+					     struct iommu_gpasid_bind_data *data)
 {
 	return -ENODEV;
 }
 
-static inline int iommu_sva_unbind_gpasid(struct iommu_domain *domain,
-					   struct device *dev, int pasid)
+static inline int iommu_uapi_sva_unbind_gpasid(struct iommu_domain *domain,
+					       struct device *dev, int pasid)
 {
 	return -ENODEV;
 }
-- 
2.7.4

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

^ permalink raw reply	[flat|nested] 17+ messages in thread

* [PATCH v9 6/7] iommu/uapi: Handle data and argsz filled by users
  2020-09-11 21:57 [PATCH v9 0/7] IOMMU user API enhancement Jacob Pan
                   ` (4 preceding siblings ...)
  2020-09-11 21:57 ` [PATCH v9 5/7] iommu/uapi: Rename uapi functions Jacob Pan
@ 2020-09-11 21:57 ` Jacob Pan
  2020-09-11 21:57 ` [PATCH v9 7/7] iommu/vt-d: Check UAPI data processed by IOMMU core Jacob Pan
  2020-09-18 10:02 ` [PATCH v9 0/7] IOMMU user API enhancement Joerg Roedel
  7 siblings, 0 replies; 17+ messages in thread
From: Jacob Pan @ 2020-09-11 21:57 UTC (permalink / raw)
  To: iommu, LKML, Joerg Roedel, Alex Williamson, Lu Baolu,
	David Woodhouse, Jonathan Corbet
  Cc: Tian, Kevin, Raj Ashok, Yi Sun, Jean-Philippe Brucker, Wu Hao

IOMMU user APIs are responsible for processing user data. This patch
changes the interface such that user pointers can be passed into IOMMU
code directly. Separate kernel APIs without user pointers are introduced
for in-kernel users of the UAPI functionality.

IOMMU UAPI data has a user filled argsz field which indicates the data
length of the structure. User data is not trusted, argsz must be
validated based on the current kernel data size, mandatory data size,
and feature flags.

User data may also be extended, resulting in possible argsz increase.
Backward compatibility is ensured based on size and flags (or
the functional equivalent fields) checking.

This patch adds sanity checks in the IOMMU layer. In addition to argsz,
reserved/unused fields in padding, flags, and version are also checked.
Details are documented in Documentation/userspace-api/iommu.rst

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 | 199 ++++++++++++++++++++++++++++++++++++++++++++++++--
 include/linux/iommu.h |  28 ++++---
 2 files changed, 211 insertions(+), 16 deletions(-)

diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index 4ae02291ccc2..5c1b7ae48aae 100644
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -1961,34 +1961,219 @@ int iommu_attach_device(struct iommu_domain *domain, struct device *dev)
 }
 EXPORT_SYMBOL_GPL(iommu_attach_device);
 
+/*
+ * Check flags and other user provided data for valid combinations. We also
+ * make sure no reserved fields or unused flags are set. This is to ensure
+ * not breaking userspace in the future when these fields or flags are used.
+ */
+static int iommu_check_cache_invl_data(struct iommu_cache_invalidate_info *info)
+{
+	u32 mask;
+	int i;
+
+	if (info->version != IOMMU_CACHE_INVALIDATE_INFO_VERSION_1)
+		return -EINVAL;
+
+	mask = (1 << IOMMU_CACHE_INV_TYPE_NR) - 1;
+	if (info->cache & ~mask)
+		return -EINVAL;
+
+	if (info->granularity >= IOMMU_INV_GRANU_NR)
+		return -EINVAL;
+
+	switch (info->granularity) {
+	case IOMMU_INV_GRANU_ADDR:
+		if (info->cache & IOMMU_CACHE_INV_TYPE_PASID)
+			return -EINVAL;
+
+		mask = IOMMU_INV_ADDR_FLAGS_PASID |
+			IOMMU_INV_ADDR_FLAGS_ARCHID |
+			IOMMU_INV_ADDR_FLAGS_LEAF;
+
+		if (info->granu.addr_info.flags & ~mask)
+			return -EINVAL;
+		break;
+	case IOMMU_INV_GRANU_PASID:
+		mask = IOMMU_INV_PASID_FLAGS_PASID |
+			IOMMU_INV_PASID_FLAGS_ARCHID;
+		if (info->granu.pasid_info.flags & ~mask)
+			return -EINVAL;
+
+		break;
+	case IOMMU_INV_GRANU_DOMAIN:
+		if (info->cache & IOMMU_CACHE_INV_TYPE_DEV_IOTLB)
+			return -EINVAL;
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	/* Check reserved padding fields */
+	for (i = 0; i < sizeof(info->padding); i++) {
+		if (info->padding[i])
+			return -EINVAL;
+	}
+
+	return 0;
+}
+
 int iommu_uapi_cache_invalidate(struct iommu_domain *domain, struct device *dev,
-				struct iommu_cache_invalidate_info *inv_info)
+				void __user *uinfo)
 {
+	struct iommu_cache_invalidate_info inv_info = { 0 };
+	u32 minsz;
+	int ret = 0;
+
 	if (unlikely(!domain->ops->cache_invalidate))
 		return -ENODEV;
 
-	return domain->ops->cache_invalidate(domain, dev, inv_info);
+	/*
+	 * No new spaces can be added before the variable sized union, the
+	 * minimum size is the offset to the union.
+	 */
+	minsz = offsetof(struct iommu_cache_invalidate_info, granu);
+
+	/* Copy minsz from user to get flags and argsz */
+	if (copy_from_user(&inv_info, uinfo, minsz))
+		return -EFAULT;
+
+	/* Fields before variable size union is mandatory */
+	if (inv_info.argsz < minsz)
+		return -EINVAL;
+
+	/* PASID and address granu require additional info beyond minsz */
+	if (inv_info.argsz == minsz &&
+	    ((inv_info.granularity == IOMMU_INV_GRANU_PASID) ||
+		    (inv_info.granularity == IOMMU_INV_GRANU_ADDR)))
+		return -EINVAL;
+
+	if (inv_info.granularity == IOMMU_INV_GRANU_PASID &&
+	    inv_info.argsz < offsetofend(struct iommu_cache_invalidate_info, granu.pasid_info))
+		return -EINVAL;
+
+	if (inv_info.granularity == IOMMU_INV_GRANU_ADDR &&
+	    inv_info.argsz < offsetofend(struct iommu_cache_invalidate_info, granu.addr_info))
+		return -EINVAL;
+
+	/*
+	 * User might be using a newer UAPI header which has a larger data
+	 * size, we shall support the existing flags within the current
+	 * size. Copy the remaining user data _after_ minsz but not more
+	 * than the current kernel supported size.
+	 */
+	if (copy_from_user((void *)&inv_info + minsz, uinfo + minsz,
+			   min_t(u32, inv_info.argsz, sizeof(inv_info)) - minsz))
+		return -EFAULT;
+
+	/* Now the argsz is validated, check the content */
+	ret = iommu_check_cache_invl_data(&inv_info);
+	if (ret)
+		return ret;
+
+	return domain->ops->cache_invalidate(domain, dev, &inv_info);
 }
 EXPORT_SYMBOL_GPL(iommu_uapi_cache_invalidate);
 
-int iommu_uapi_sva_bind_gpasid(struct iommu_domain *domain,
-			       struct device *dev, struct iommu_gpasid_bind_data *data)
+static int iommu_check_bind_data(struct iommu_gpasid_bind_data *data)
+{
+	u32 mask;
+	int i;
+
+	if (data->version != IOMMU_GPASID_BIND_VERSION_1)
+		return -EINVAL;
+
+	/* Check the range of supported formats */
+	if (data->format >= IOMMU_PASID_FORMAT_LAST)
+		return -EINVAL;
+
+	/* Check all flags */
+	mask = IOMMU_SVA_GPASID_VAL;
+	if (data->flags & ~mask)
+		return -EINVAL;
+
+	/* Check reserved padding fields */
+	for (i = 0; i < sizeof(data->padding); i++) {
+		if (data->padding[i])
+			return -EINVAL;
+	}
+
+	return 0;
+}
+
+static int iommu_sva_prepare_bind_data(void __user *udata,
+				       struct iommu_gpasid_bind_data *data)
 {
+	u32 minsz;
+
+	/*
+	 * No new spaces can be added before the variable sized union, the
+	 * minimum size is the offset to the union.
+	 */
+	minsz = offsetof(struct iommu_gpasid_bind_data, vendor);
+
+	/* Copy minsz from user to get flags and argsz */
+	if (copy_from_user(data, udata, minsz))
+		return -EFAULT;
+
+	/* Fields before variable size union is mandatory */
+	if (data->argsz < minsz)
+		return -EINVAL;
+	/*
+	 * User might be using a newer UAPI header, we shall let IOMMU vendor
+	 * driver decide on what size it needs. Since the guest PASID bind data
+	 * can be vendor specific, larger argsz could be the result of extension
+	 * for one vendor but it should not affect another vendor.
+	 * Copy the remaining user data _after_ minsz
+	 */
+	if (copy_from_user((void *)data + minsz, udata + minsz,
+			   min_t(u32, data->argsz, sizeof(*data)) - minsz))
+		return -EFAULT;
+
+	return iommu_check_bind_data(data);
+}
+
+int iommu_uapi_sva_bind_gpasid(struct iommu_domain *domain, struct device *dev,
+			       void __user *udata)
+{
+	struct iommu_gpasid_bind_data data = { 0 };
+	int ret;
+
 	if (unlikely(!domain->ops->sva_bind_gpasid))
 		return -ENODEV;
 
-	return domain->ops->sva_bind_gpasid(domain, dev, data);
+	ret = iommu_sva_prepare_bind_data(udata, &data);
+	if (ret)
+		return ret;
+
+	return domain->ops->sva_bind_gpasid(domain, dev, &data);
 }
 EXPORT_SYMBOL_GPL(iommu_uapi_sva_bind_gpasid);
 
-int iommu_uapi_sva_unbind_gpasid(struct iommu_domain *domain, struct device *dev,
-				 ioasid_t pasid)
+int iommu_sva_unbind_gpasid(struct iommu_domain *domain, struct device *dev,
+			     ioasid_t pasid)
 {
 	if (unlikely(!domain->ops->sva_unbind_gpasid))
 		return -ENODEV;
 
 	return domain->ops->sva_unbind_gpasid(dev, pasid);
 }
+EXPORT_SYMBOL_GPL(iommu_sva_unbind_gpasid);
+
+int iommu_uapi_sva_unbind_gpasid(struct iommu_domain *domain, struct device *dev,
+				 void __user *udata)
+{
+	struct iommu_gpasid_bind_data data = { 0 };
+	int ret;
+
+	if (unlikely(!domain->ops->sva_bind_gpasid))
+		return -ENODEV;
+
+	ret = iommu_sva_prepare_bind_data(udata, &data);
+	if (ret)
+		return ret;
+
+	return iommu_sva_unbind_gpasid(domain, dev, data.hpasid);
+}
 EXPORT_SYMBOL_GPL(iommu_uapi_sva_unbind_gpasid);
 
 static void __iommu_detach_device(struct iommu_domain *domain,
diff --git a/include/linux/iommu.h b/include/linux/iommu.h
index 710d5d2691eb..3ca3a40fc80f 100644
--- a/include/linux/iommu.h
+++ b/include/linux/iommu.h
@@ -426,11 +426,14 @@ extern void iommu_detach_device(struct iommu_domain *domain,
 				struct device *dev);
 extern int iommu_uapi_cache_invalidate(struct iommu_domain *domain,
 				       struct device *dev,
-				       struct iommu_cache_invalidate_info *inv_info);
+				       void __user *uinfo);
+
 extern int iommu_uapi_sva_bind_gpasid(struct iommu_domain *domain,
-				      struct device *dev, struct iommu_gpasid_bind_data *data);
+				      struct device *dev, void __user *udata);
 extern int iommu_uapi_sva_unbind_gpasid(struct iommu_domain *domain,
-					struct device *dev, ioasid_t pasid);
+					struct device *dev, void __user *udata);
+extern int iommu_sva_unbind_gpasid(struct iommu_domain *domain,
+				   struct device *dev, ioasid_t pasid);
 extern struct iommu_domain *iommu_get_domain_for_dev(struct device *dev);
 extern struct iommu_domain *iommu_get_dma_domain(struct device *dev);
 extern int iommu_map(struct iommu_domain *domain, unsigned long iova,
@@ -1032,22 +1035,29 @@ static inline int iommu_sva_get_pasid(struct iommu_sva *handle)
 	return IOMMU_PASID_INVALID;
 }
 
-static inline int iommu_uapi_cache_invalidate(struct iommu_domain *domain,
-					      struct device *dev,
-					      struct iommu_cache_invalidate_info *inv_info)
+static inline int
+iommu_uapi_cache_invalidate(struct iommu_domain *domain,
+			    struct device *dev,
+			    struct iommu_cache_invalidate_info *inv_info)
 {
 	return -ENODEV;
 }
 
 static inline int iommu_uapi_sva_bind_gpasid(struct iommu_domain *domain,
-					     struct device *dev,
-					     struct iommu_gpasid_bind_data *data)
+					     struct device *dev, void __user *udata)
 {
 	return -ENODEV;
 }
 
 static inline int iommu_uapi_sva_unbind_gpasid(struct iommu_domain *domain,
-					       struct device *dev, int pasid)
+					       struct device *dev, void __user *udata)
+{
+	return -ENODEV;
+}
+
+static inline int iommu_sva_unbind_gpasid(struct iommu_domain *domain,
+					  struct device *dev,
+					  ioasid_t pasid)
 {
 	return -ENODEV;
 }
-- 
2.7.4

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^ permalink raw reply	[flat|nested] 17+ messages in thread

* [PATCH v9 7/7] iommu/vt-d: Check UAPI data processed by IOMMU core
  2020-09-11 21:57 [PATCH v9 0/7] IOMMU user API enhancement Jacob Pan
                   ` (5 preceding siblings ...)
  2020-09-11 21:57 ` [PATCH v9 6/7] iommu/uapi: Handle data and argsz filled by users Jacob Pan
@ 2020-09-11 21:57 ` Jacob Pan
  2020-09-18 10:02 ` [PATCH v9 0/7] IOMMU user API enhancement Joerg Roedel
  7 siblings, 0 replies; 17+ messages in thread
From: Jacob Pan @ 2020-09-11 21:57 UTC (permalink / raw)
  To: iommu, LKML, Joerg Roedel, Alex Williamson, Lu Baolu,
	David Woodhouse, Jonathan Corbet
  Cc: Tian, Kevin, Raj Ashok, Yi Sun, Jean-Philippe Brucker, Wu Hao

IOMMU generic layer already does sanity checks on UAPI data for version
match and argsz range based on generic information.

This patch adjusts the following data checking responsibilities:
- removes the redundant version check from VT-d driver
- removes the check for vendor specific data size
- adds check for the use of reserved/undefined flags

Signed-off-by: Jacob Pan <jacob.jun.pan@linux.intel.com>
---
 drivers/iommu/intel/iommu.c |  3 +--
 drivers/iommu/intel/svm.c   | 11 +++++++++--
 include/uapi/linux/iommu.h  |  1 +
 3 files changed, 11 insertions(+), 4 deletions(-)

diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
index 461f3a6864d4..18ed3b3c70d7 100644
--- a/drivers/iommu/intel/iommu.c
+++ b/drivers/iommu/intel/iommu.c
@@ -5408,8 +5408,7 @@ intel_iommu_sva_invalidate(struct iommu_domain *domain, struct device *dev,
 	int ret = 0;
 	u64 size = 0;
 
-	if (!inv_info || !dmar_domain ||
-	    inv_info->version != IOMMU_CACHE_INVALIDATE_INFO_VERSION_1)
+	if (!inv_info || !dmar_domain)
 		return -EINVAL;
 
 	if (!dev || !dev_is_pci(dev))
diff --git a/drivers/iommu/intel/svm.c b/drivers/iommu/intel/svm.c
index 99353d6468fa..0cb9a15f1112 100644
--- a/drivers/iommu/intel/svm.c
+++ b/drivers/iommu/intel/svm.c
@@ -284,8 +284,15 @@ int intel_svm_bind_gpasid(struct iommu_domain *domain, struct device *dev,
 	if (WARN_ON(!iommu) || !data)
 		return -EINVAL;
 
-	if (data->version != IOMMU_GPASID_BIND_VERSION_1 ||
-	    data->format != IOMMU_PASID_FORMAT_INTEL_VTD)
+	if (data->format != IOMMU_PASID_FORMAT_INTEL_VTD)
+		return -EINVAL;
+
+	/* IOMMU core ensures argsz is more than the start of the union */
+	if (data->argsz < offsetofend(struct iommu_gpasid_bind_data, vendor.vtd))
+		return -EINVAL;
+
+	/* Make sure no undefined flags are used in vendor data */
+	if (data->vendor.vtd.flags & ~(IOMMU_SVA_VTD_GPASID_LAST - 1))
 		return -EINVAL;
 
 	if (!dev_is_pci(dev))
diff --git a/include/uapi/linux/iommu.h b/include/uapi/linux/iommu.h
index c64bca5af419..1ebc23df4fbc 100644
--- a/include/uapi/linux/iommu.h
+++ b/include/uapi/linux/iommu.h
@@ -288,6 +288,7 @@ struct iommu_gpasid_bind_data_vtd {
 #define IOMMU_SVA_VTD_GPASID_PWT	(1 << 3) /* page-level write through */
 #define IOMMU_SVA_VTD_GPASID_EMTE	(1 << 4) /* extended mem type enable */
 #define IOMMU_SVA_VTD_GPASID_CD		(1 << 5) /* PASID-level cache disable */
+#define IOMMU_SVA_VTD_GPASID_LAST	(1 << 6)
 	__u64 flags;
 	__u32 pat;
 	__u32 emt;
-- 
2.7.4

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^ permalink raw reply	[flat|nested] 17+ messages in thread

* Re: [PATCH v9 1/7] docs: IOMMU user API
  2020-09-11 21:57 ` [PATCH v9 1/7] docs: IOMMU user API Jacob Pan
@ 2020-09-16 18:26   ` Randy Dunlap
  2020-09-18 19:44     ` Jacob Pan
  0 siblings, 1 reply; 17+ messages in thread
From: Randy Dunlap @ 2020-09-16 18:26 UTC (permalink / raw)
  To: Jacob Pan, iommu, LKML, Joerg Roedel, Alex Williamson, Lu Baolu,
	David Woodhouse, Jonathan Corbet
  Cc: Tian, Kevin, Raj Ashok, Yi Sun, Jean-Philippe Brucker, Wu Hao

On 9/11/20 2:57 PM, Jacob Pan wrote:
> IOMMU UAPI is newly introduced to support communications between guest
> virtual IOMMU and host IOMMU. There has been lots of discussions on how
> it should work with VFIO UAPI and userspace in general.
> 
> This document is intended to clarify the UAPI design and usage. The
> mechanics of how future extensions should be achieved are also covered
> in this documentation.
> 
> Reviewed-by: Eric Auger <eric.auger@redhat.com>
> Signed-off-by: Liu Yi L <yi.l.liu@intel.com>
> Signed-off-by: Jacob Pan <jacob.jun.pan@linux.intel.com>
> ---
>  Documentation/userspace-api/iommu.rst | 211 ++++++++++++++++++++++++++++++++++
>  MAINTAINERS                           |   1 +
>  2 files changed, 212 insertions(+)
>  create mode 100644 Documentation/userspace-api/iommu.rst

Hi,
I have a few edit changes for you below:


> diff --git a/Documentation/userspace-api/iommu.rst b/Documentation/userspace-api/iommu.rst
> new file mode 100644
> index 000000000000..1e68e8f05bb3
> --- /dev/null
> +++ b/Documentation/userspace-api/iommu.rst
> @@ -0,0 +1,211 @@
> +.. SPDX-License-Identifier: GPL-2.0
> +.. iommu:
> +
> +=====================================
> +IOMMU Userspace API
> +=====================================
> +
> +IOMMU UAPI is used for virtualization cases where communications are
> +needed between physical and virtual IOMMU drivers. For baremetal
> +usage, the IOMMU is a system device which does not need to communicate
> +with user space directly.

        userspace

for consistency

> +
> +The primary use cases are guest Shared Virtual Address (SVA) and
> +guest IO virtual address (IOVA), wherin the vIOMMU implementation

                                    wherein

> +relies on the physical IOMMU and for this reason requires interactions
> +with the host driver.
> +
> +.. contents:: :local:
> +
> +Functionalities
> +===============
> +Communications of user and kernel involve both directions. The
> +supported user-kernel APIs are as follows:
> +
> +1. Alloc/Free PASID
> +2. Bind/Unbind guest PASID (e.g. Intel VT-d)
> +3. Bind/Unbind guest PASID table (e.g. ARM SMMU)
> +4. Invalidate IOMMU caches upon guest requests
> +5. Report errors to the guest and serve page requests
> +
> +Requirements
> +============
> +The IOMMU UAPIs are generic and extensible to meet the following
> +requirements:
> +
> +1. Emulated and para-virtualised vIOMMUs
> +2. Multiple vendors (Intel VT-d, ARM SMMU, etc.)
> +3. Extensions to the UAPI shall not break existing user space

                                                      userspace

> +
> +Interfaces
> +==========
> +Although the data structures defined in IOMMU UAPI are self-contained,
> +there is no user API functions introduced. Instead, IOMMU UAPI is

   there are no

> +designed to work with existing user driver frameworks such as VFIO.
> +
> +Extension Rules & Precautions
> +-----------------------------
> +When IOMMU UAPI gets extended, the data structures can *only* be
> +modified in two ways:
> +
> +1. Adding new fields by re-purposing the padding[] field. No size change.
> +2. Adding new union members at the end. May increase the structure sizes.
> +
> +No new fields can be added *after* the variable sized union in that it
> +will break backward compatibility when offset moves. A new flag must
> +be introduced whenever a change affects the structure using either
> +method. The IOMMU driver processes the data based on flags which
> +ensures backward compatibility.
> +
> +Version field is only reserved for the unlikely event of UAPI upgrade
> +at its entirety.
> +
> +It's *always* the caller's responsibility to indicate the size of the
> +structure passed by setting argsz appropriately.
> +Though at the same time, argsz is user provided data which is not
> +trusted. The argsz field allows the user app to indicate how much data
> +it is providing, it's still the kernel's responsibility to validate

         providing;

> +whether it's correct and sufficient for the requested operation.
> +
> +Compatibility Checking
> +----------------------
> +When IOMMU UAPI extension results in some structure size increase,
> +IOMMU UAPI code shall handle the following cases:
> +
> +1. User and kernel has exact size match
> +2. An older user with older kernel header (smaller UAPI size) running on a
> +   newer kernel (larger UAPI size)
> +3. A newer user with newer kernel header (larger UAPI size) running
> +   on an older kernel.
> +4. A malicious/misbehaving user pass illegal/invalid size but within

                                   passing

> +   range. The data may contain garbage.
> +
> +Feature Checking
> +----------------
> +While launching a guest with vIOMMU, it is strongly advised to check
> +the compatibility upfront, as some subsequent errors happening during
> +vIOMMU operation, such as cache invalidation failures cannot be nicely> +escaladated to the guest due to IOMMU specifications. This can lead to

   escalated

> +catastrophic failures for the users.
> +
> +User applications such as QEMU are expected to import kernel UAPI
> +headers. Backward compatibility is supported per feature flags.
> +For example, an older QEMU (with older kernel header) can run on newer
> +kernel. Newer QEMU (with new kernel header) may refuse to initialize
> +on an older kernel if new feature flags are not supported by older
> +kernel. Simply recompiling existing code with newer kernel header should
> +not be an issue in that only existing flags are used.
> +
> +IOMMU vendor driver should report the below features to IOMMU UAPI
> +consumers (e.g. via VFIO).
> +
> +1. IOMMU_NESTING_FEAT_SYSWIDE_PASID
> +2. IOMMU_NESTING_FEAT_BIND_PGTBL
> +3. IOMMU_NESTING_FEAT_BIND_PASID_TABLE
> +4. IOMMU_NESTING_FEAT_CACHE_INVLD
> +5. IOMMU_NESTING_FEAT_PAGE_REQUEST
> +
> +Take VFIO as example, upon request from VFIO user space (e.g. QEMU),

                                                userspace

> +VFIO kernel code shall query IOMMU vendor driver for the support of
> +the above features. Query result can then be reported back to the
> +user-space caller. Details can be found in

   userspace

> +Documentation/driver-api/vfio.rst.
> +
> +
> +Data Passing Example with VFIO
> +------------------------------
> +As the ubiquitous userspace driver framework, VFIO is already IOMMU
> +aware and shares many key concepts such as device model, group, and
> +protection domain. Other user driver frameworks can also be extended
> +to support IOMMU UAPI but it is outside the scope of this document.
> +
> +In this tight-knit VFIO-IOMMU interface, the ultimate consumer of the
> +IOMMU UAPI data is the host IOMMU driver. VFIO facilitates user-kernel
> +transport, capability checking, security, and life cycle management of
> +process address space ID (PASID).
> +
> +VFIO layer conveys the data structures down to the IOMMU driver, it

                                                            driver. It

> +follows the pattern below::
> +
> +   struct {
> +	__u32 argsz;
> +	__u32 flags;
> +	__u8  data[];
> +   };
> +
> +Here data[] contains the IOMMU UAPI data structures. VFIO has the
> +freedom to bundle the data as well as parse data size based on its own flags.
> +
> +In order to determine the size and feature set of the user data, argsz
> +and flags (or the equivalent) are also embedded in the IOMMU UAPI data
> +structures.
> +
> +A "__u32 argsz" field is *always* at the beginning of each structure.
> +
> +For example:
> +::
> +
> +   struct iommu_cache_invalidate_info {
> +	__u32	argsz;
> +	#define IOMMU_CACHE_INVALIDATE_INFO_VERSION_1 1
> +	__u32	version;
> +	/* IOMMU paging structure cache */
> +	#define IOMMU_CACHE_INV_TYPE_IOTLB	(1 << 0) /* IOMMU IOTLB */
> +	#define IOMMU_CACHE_INV_TYPE_DEV_IOTLB	(1 << 1) /* Device IOTLB */
> +	#define IOMMU_CACHE_INV_TYPE_PASID	(1 << 2) /* PASID cache */
> +	#define IOMMU_CACHE_INV_TYPE_NR		(3)
> +	__u8	cache;
> +	__u8	granularity;
> +	__u8	padding[6];
> +	union {
> +		struct iommu_inv_pasid_info pasid_info;
> +		struct iommu_inv_addr_info addr_info;
> +	} granu;
> +   };
> +
> +VFIO is responsible for checking its own argsz and flags. It then
> +invokes appropriate IOMMU UAPI functions. The user pointers are passed
> +to the IOMMU layer for further processing. The responsibilities are
> +divided as follows:
> +
> +- Generic IOMMU layer checks argsz range based on UAPI data in the
> +  current kernel version

                    version.

> +
> +- Generic IOMMU layer checks content of the UAPI data for non-zero
> +  reserved bits in flags, padding fields, and unsupported version.
> +  This is to ensure not breaking userspace in the future when these
> +  fields or flags are used.
> +
> +- Vendor IOMMU driver checks argsz based on vendor flags, UAPI data

                                                      flags. UAPI data

> +  is consumed based on flags. Vendor driver has access to
> +  unadulterated argsz value in case of vendor specific future
> +  extensions. Currently, it does not perform the copy_from_user()
> +  itself. A __user pointer can be provided in some future scenarios
> +  where there's vendor data outside of the structure definition.
> +
> +IOMMU code treats UAPI data into two categories:

                                in

> +
> +- structure contains vendor data
> +  (Example: iommu_uapi_cache_invalidate())
> +
> +- structure contains only generic data
> +  (Example: iommu_uapi_sva_bind_gpasid())
> +
> +
> +
> +Sharing UAPI with in-kernel users
> +---------------------------------
> +For UAPIs that are shared with in-kernel users, a wrapper function is
> +provided to distinguish the callers. For example,
> +
> +Userspace caller ::
> +
> +  int iommu_uapi_sva_unbind_gpasid(struct iommu_domain *domain,
> +                                   struct device *dev,
> +                                   void __user *udata)
> +
> +In-kernel caller ::
> +
> +  int iommu_sva_unbind_gpasid(struct iommu_domain *domain,
> +                                   struct device *dev,
> +                                   struct iommu_gpasid_bind_data *data)


thanks.
-- 
~Randy

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^ permalink raw reply	[flat|nested] 17+ messages in thread

* Re: [PATCH v9 3/7] iommu/uapi: Introduce enum type for PASID data format
  2020-09-11 21:57 ` [PATCH v9 3/7] iommu/uapi: Introduce enum type for PASID data format Jacob Pan
@ 2020-09-18  9:44   ` Joerg Roedel
  2020-09-18 17:11     ` Jacob Pan
  0 siblings, 1 reply; 17+ messages in thread
From: Joerg Roedel @ 2020-09-18  9:44 UTC (permalink / raw)
  To: Jacob Pan
  Cc: Tian, Kevin, Raj Ashok, Jonathan Corbet, Jean-Philippe Brucker,
	Alex Williamson, LKML, iommu, Wu Hao, David Woodhouse, Yi Sun

On Fri, Sep 11, 2020 at 02:57:52PM -0700, Jacob Pan wrote:
> There can be multiple vendor-specific PASID data formats used in UAPI
> structures. This patch adds enum type with a last entry which makes
> range checking much easier.

But it also makes it much easier to screw up the numbers (which are ABI)
by inserting a new value into the middle. I prefer defines here, or
alternativly BUILD_BUG_ON() checks for the numbers.

Regards,

	Joerg

> 
> Suggested-by: Alex Williamson <alex.williamson@redhat.com>
> Reviewed-by: Eric Auger <eric.auger@redhat.com>
> Signed-off-by: Jacob Pan <jacob.jun.pan@linux.intel.com>
> ---
>  include/uapi/linux/iommu.h | 8 ++++++--
>  1 file changed, 6 insertions(+), 2 deletions(-)
> 
> diff --git a/include/uapi/linux/iommu.h b/include/uapi/linux/iommu.h
> index b42acc8fe007..7cc6ee6c41f7 100644
> --- a/include/uapi/linux/iommu.h
> +++ b/include/uapi/linux/iommu.h
> @@ -298,11 +298,16 @@ struct iommu_gpasid_bind_data_vtd {
>  					 IOMMU_SVA_VTD_GPASID_PCD |  \
>  					 IOMMU_SVA_VTD_GPASID_PWT)
>  
> +enum iommu_pasid_data_format {
> +	IOMMU_PASID_FORMAT_INTEL_VTD = 1,
> +	IOMMU_PASID_FORMAT_LAST,
> +};
> +
>  /**
>   * 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
> + * @format:	PASID table entry format of enum iommu_pasid_data_format type
>   * @flags:	Additional information on guest bind request
>   * @gpgd:	Guest page directory base of the guest mm to bind
>   * @hpasid:	Process address space ID used for the guest mm in host IOMMU
> @@ -321,7 +326,6 @@ struct iommu_gpasid_bind_data {
>  	__u32 argsz;
>  #define IOMMU_GPASID_BIND_VERSION_1	1
>  	__u32 version;
> -#define IOMMU_PASID_FORMAT_INTEL_VTD	1
>  	__u32 format;
>  	__u32 addr_width;
>  #define IOMMU_SVA_GPASID_VAL	(1 << 0) /* guest PASID valid */
> -- 
> 2.7.4
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^ permalink raw reply	[flat|nested] 17+ messages in thread

* Re: [PATCH v9 0/7] IOMMU user API enhancement
  2020-09-11 21:57 [PATCH v9 0/7] IOMMU user API enhancement Jacob Pan
                   ` (6 preceding siblings ...)
  2020-09-11 21:57 ` [PATCH v9 7/7] iommu/vt-d: Check UAPI data processed by IOMMU core Jacob Pan
@ 2020-09-18 10:02 ` Joerg Roedel
  2020-09-18 17:26   ` Jacob Pan
  7 siblings, 1 reply; 17+ messages in thread
From: Joerg Roedel @ 2020-09-18 10:02 UTC (permalink / raw)
  To: Jacob Pan
  Cc: Tian, Kevin, Raj Ashok, Jonathan Corbet, Jean-Philippe Brucker,
	Alex Williamson, LKML, iommu, Wu Hao, David Woodhouse, Yi Sun

Hi Jacob,

On Fri, Sep 11, 2020 at 02:57:49PM -0700, Jacob Pan wrote:
> IOMMU user API header was introduced to support nested DMA translation and
> related fault handling. The current UAPI data structures consist of three
> areas that cover the interactions between host kernel and guest:
>  - fault handling
>  - cache invalidation
>  - bind guest page tables, i.e. guest PASID
> 
> Future extensions are likely to support more architectures and vIOMMU features.
> 
> In the previous discussion, using user-filled data size and feature flags is
> made a preferred approach over a unified version number.
> https://lkml.org/lkml/2020/1/29/45
> 
> In addition to introduce argsz field to data structures, this patchset is also
> trying to document the UAPI design, usage, and extension rules. VT-d driver
> changes to utilize the new argsz field is included, VFIO usage is to follow.
> 
> This set is available at:
> https://github.com/jacobpan/linux.git vsva_v5.9_uapi_v9

This changes user visible structs in incompatible ways, are you sure
those are not used yet anywhere?

Please address Randy's comments on patch 1 and my comment about the
build-time checking and repost with linux-api@vger.kernel.org on Cc.

Regards,

	Joerg
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^ permalink raw reply	[flat|nested] 17+ messages in thread

* Re: [PATCH v9 3/7] iommu/uapi: Introduce enum type for PASID data format
  2020-09-18  9:44   ` Joerg Roedel
@ 2020-09-18 17:11     ` Jacob Pan
  2020-09-22 20:24       ` Jacob Pan
  2020-09-24  8:40       ` Joerg Roedel
  0 siblings, 2 replies; 17+ messages in thread
From: Jacob Pan @ 2020-09-18 17:11 UTC (permalink / raw)
  To: Joerg Roedel
  Cc: Tian, Kevin, Jacob Pan, Raj Ashok, Jonathan Corbet,
	Jean-Philippe Brucker, iommu, LKML, Alex Williamson, Wu Hao,
	David Woodhouse, Yi Sun

Hi Joerg,

On Fri, 18 Sep 2020 11:44:50 +0200, Joerg Roedel <joro@8bytes.org> wrote:

> On Fri, Sep 11, 2020 at 02:57:52PM -0700, Jacob Pan wrote:
> > There can be multiple vendor-specific PASID data formats used in UAPI
> > structures. This patch adds enum type with a last entry which makes
> > range checking much easier.  
> 
> But it also makes it much easier to screw up the numbers (which are ABI)
> by inserting a new value into the middle. I prefer defines here, or
> alternativly BUILD_BUG_ON() checks for the numbers.
> 
I am not following, the purpose of IOMMU_PASID_FORMAT_LAST *is* for
preparing the future insertion of new value into the middle.
The checking against IOMMU_PASID_FORMAT_LAST is to protect ABI
compatibility by making sure that out of range format are rejected in all
versions of the ABI.
For example, in v5.10, ABI has IOMMU_PASID_FORMAT_LAST = 2, then user data
with format = 2 will be rejected. So this user app will not work or
released.

Now say in v5.11, we add one more format in the middle and set
IOMMU_PASID_FORMAT_LAST = 3. Then user data with the new format = 2 can be supported.

Without the checking for IOMMU_PASID_FORMAT_LAST, at v5.10 time the user
binary may succeed and become legacy binary that we cannot break in v5.11.
This renders format = 2 unusable for v5.11.

I thought enum makes it less susceptible to programming errors than defines
by making sure the ascending order. I might have missed your point, could
you elaborate?

> Regards,
> 
> 	Joerg
> 
> > 
> > Suggested-by: Alex Williamson <alex.williamson@redhat.com>
> > Reviewed-by: Eric Auger <eric.auger@redhat.com>
> > Signed-off-by: Jacob Pan <jacob.jun.pan@linux.intel.com>
> > ---
> >  include/uapi/linux/iommu.h | 8 ++++++--
> >  1 file changed, 6 insertions(+), 2 deletions(-)
> > 
> > diff --git a/include/uapi/linux/iommu.h b/include/uapi/linux/iommu.h
> > index b42acc8fe007..7cc6ee6c41f7 100644
> > --- a/include/uapi/linux/iommu.h
> > +++ b/include/uapi/linux/iommu.h
> > @@ -298,11 +298,16 @@ struct iommu_gpasid_bind_data_vtd {
> >  					 IOMMU_SVA_VTD_GPASID_PCD |  \
> >  					 IOMMU_SVA_VTD_GPASID_PWT)
> >  
> > +enum iommu_pasid_data_format {
> > +	IOMMU_PASID_FORMAT_INTEL_VTD = 1,
> > +	IOMMU_PASID_FORMAT_LAST,
> > +};
> > +
> >  /**
> >   * 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
> > + * @format:	PASID table entry format of enum
> > iommu_pasid_data_format type
> >   * @flags:	Additional information on guest bind request
> >   * @gpgd:	Guest page directory base of the guest mm to bind
> >   * @hpasid:	Process address space ID used for the guest mm in
> > host IOMMU @@ -321,7 +326,6 @@ struct iommu_gpasid_bind_data {
> >  	__u32 argsz;
> >  #define IOMMU_GPASID_BIND_VERSION_1	1
> >  	__u32 version;
> > -#define IOMMU_PASID_FORMAT_INTEL_VTD	1
> >  	__u32 format;
> >  	__u32 addr_width;
> >  #define IOMMU_SVA_GPASID_VAL	(1 << 0) /* guest PASID valid */
> > -- 
> > 2.7.4  


Thanks,

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

^ permalink raw reply	[flat|nested] 17+ messages in thread

* Re: [PATCH v9 0/7] IOMMU user API enhancement
  2020-09-18 10:02 ` [PATCH v9 0/7] IOMMU user API enhancement Joerg Roedel
@ 2020-09-18 17:26   ` Jacob Pan
  0 siblings, 0 replies; 17+ messages in thread
From: Jacob Pan @ 2020-09-18 17:26 UTC (permalink / raw)
  To: Joerg Roedel
  Cc: Tian, Kevin, Jacob Pan, Raj Ashok, Jonathan Corbet,
	Jean-Philippe Brucker, iommu, LKML, Alex Williamson, Wu Hao,
	David Woodhouse, Yi Sun

Hi Joerg,

On Fri, 18 Sep 2020 12:02:36 +0200, Joerg Roedel <joro@8bytes.org> wrote:

> Hi Jacob,
> 
> On Fri, Sep 11, 2020 at 02:57:49PM -0700, Jacob Pan wrote:
> > IOMMU user API header was introduced to support nested DMA translation
> > and related fault handling. The current UAPI data structures consist of
> > three areas that cover the interactions between host kernel and guest:
> >  - fault handling
> >  - cache invalidation
> >  - bind guest page tables, i.e. guest PASID
> > 
> > Future extensions are likely to support more architectures and vIOMMU
> > features.
> > 
> > In the previous discussion, using user-filled data size and feature
> > flags is made a preferred approach over a unified version number.
> > https://lkml.org/lkml/2020/1/29/45
> > 
> > In addition to introduce argsz field to data structures, this patchset
> > is also trying to document the UAPI design, usage, and extension rules.
> > VT-d driver changes to utilize the new argsz field is included, VFIO
> > usage is to follow.
> > 
> > This set is available at:
> > https://github.com/jacobpan/linux.git vsva_v5.9_uapi_v9  
> 
> This changes user visible structs in incompatible ways, are you sure
> those are not used yet anywhere?
> 
These structs are not used yet in that IOMMU UAPI does not provide
direct user IOCTLs. For guest SVA of assigned devices, VFIO is used. Yi's
companion patches are here.
https://lore.kernel.org/linux-iommu/5dd95fbf-054c-3bbc-e76b-2d5636214ff2@redhat.com/T/#t

These user structs can also be used by other framework in the future, such
as vDPA.

> Please address Randy's comments on patch 1 and my comment about the
> build-time checking and repost with linux-api@vger.kernel.org on Cc.
> 
Will do.

> Regards,
> 
> 	Joerg


Thanks,

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

^ permalink raw reply	[flat|nested] 17+ messages in thread

* Re: [PATCH v9 1/7] docs: IOMMU user API
  2020-09-16 18:26   ` Randy Dunlap
@ 2020-09-18 19:44     ` Jacob Pan
  0 siblings, 0 replies; 17+ messages in thread
From: Jacob Pan @ 2020-09-18 19:44 UTC (permalink / raw)
  To: Randy Dunlap
  Cc: Tian, Kevin, Jacob Pan, Raj Ashok, Jonathan Corbet,
	Jean-Philippe Brucker, iommu, LKML, Alex Williamson, Wu Hao,
	David Woodhouse, Yi Sun

Hi Randy,

Thanks for the review.

On Wed, 16 Sep 2020 11:26:00 -0700, Randy Dunlap <rdunlap@infradead.org>
wrote:

> On 9/11/20 2:57 PM, Jacob Pan wrote:
> > IOMMU UAPI is newly introduced to support communications between guest
> > virtual IOMMU and host IOMMU. There has been lots of discussions on how
> > it should work with VFIO UAPI and userspace in general.
> > 
> > This document is intended to clarify the UAPI design and usage. The
> > mechanics of how future extensions should be achieved are also covered
> > in this documentation.
> > 
> > Reviewed-by: Eric Auger <eric.auger@redhat.com>
> > Signed-off-by: Liu Yi L <yi.l.liu@intel.com>
> > Signed-off-by: Jacob Pan <jacob.jun.pan@linux.intel.com>
> > ---
> >  Documentation/userspace-api/iommu.rst | 211
> > ++++++++++++++++++++++++++++++++++
> > MAINTAINERS                           |   1 + 2 files changed, 212
> > insertions(+) create mode 100644 Documentation/userspace-api/iommu.rst  
> 
> Hi,
> I have a few edit changes for you below:
> 
> 
> > diff --git a/Documentation/userspace-api/iommu.rst
> > b/Documentation/userspace-api/iommu.rst new file mode 100644
> > index 000000000000..1e68e8f05bb3
> > --- /dev/null
> > +++ b/Documentation/userspace-api/iommu.rst
> > @@ -0,0 +1,211 @@
> > +.. SPDX-License-Identifier: GPL-2.0
> > +.. iommu:
> > +
> > +=====================================
> > +IOMMU Userspace API
> > +=====================================
> > +
> > +IOMMU UAPI is used for virtualization cases where communications are
> > +needed between physical and virtual IOMMU drivers. For baremetal
> > +usage, the IOMMU is a system device which does not need to communicate
> > +with user space directly.  
> 
>         userspace
> 
> for consistency
> 
got it

> > +
> > +The primary use cases are guest Shared Virtual Address (SVA) and
> > +guest IO virtual address (IOVA), wherin the vIOMMU implementation  
> 
>                                     wherein
> 
right

> > +relies on the physical IOMMU and for this reason requires interactions
> > +with the host driver.
> > +
> > +.. contents:: :local:
> > +
> > +Functionalities
> > +===============
> > +Communications of user and kernel involve both directions. The
> > +supported user-kernel APIs are as follows:
> > +
> > +1. Alloc/Free PASID
> > +2. Bind/Unbind guest PASID (e.g. Intel VT-d)
> > +3. Bind/Unbind guest PASID table (e.g. ARM SMMU)
> > +4. Invalidate IOMMU caches upon guest requests
> > +5. Report errors to the guest and serve page requests
> > +
> > +Requirements
> > +============
> > +The IOMMU UAPIs are generic and extensible to meet the following
> > +requirements:
> > +
> > +1. Emulated and para-virtualised vIOMMUs
> > +2. Multiple vendors (Intel VT-d, ARM SMMU, etc.)
> > +3. Extensions to the UAPI shall not break existing user space  
> 
>                                                       userspace
> 
ditto

> > +
> > +Interfaces
> > +==========
> > +Although the data structures defined in IOMMU UAPI are self-contained,
> > +there is no user API functions introduced. Instead, IOMMU UAPI is  
> 
>    there are no
> 
right

> > +designed to work with existing user driver frameworks such as VFIO.
> > +
> > +Extension Rules & Precautions
> > +-----------------------------
> > +When IOMMU UAPI gets extended, the data structures can *only* be
> > +modified in two ways:
> > +
> > +1. Adding new fields by re-purposing the padding[] field. No size
> > change. +2. Adding new union members at the end. May increase the
> > structure sizes. +
> > +No new fields can be added *after* the variable sized union in that it
> > +will break backward compatibility when offset moves. A new flag must
> > +be introduced whenever a change affects the structure using either
> > +method. The IOMMU driver processes the data based on flags which
> > +ensures backward compatibility.
> > +
> > +Version field is only reserved for the unlikely event of UAPI upgrade
> > +at its entirety.
> > +
> > +It's *always* the caller's responsibility to indicate the size of the
> > +structure passed by setting argsz appropriately.
> > +Though at the same time, argsz is user provided data which is not
> > +trusted. The argsz field allows the user app to indicate how much data
> > +it is providing, it's still the kernel's responsibility to validate  
> 
>          providing;
> 
yes. good separation.

> > +whether it's correct and sufficient for the requested operation.
> > +
> > +Compatibility Checking
> > +----------------------
> > +When IOMMU UAPI extension results in some structure size increase,
> > +IOMMU UAPI code shall handle the following cases:
> > +
> > +1. User and kernel has exact size match
> > +2. An older user with older kernel header (smaller UAPI size) running
> > on a
> > +   newer kernel (larger UAPI size)
> > +3. A newer user with newer kernel header (larger UAPI size) running
> > +   on an older kernel.
> > +4. A malicious/misbehaving user pass illegal/invalid size but within  
> 
>                                    passing
> 
got it

> > +   range. The data may contain garbage.
> > +
> > +Feature Checking
> > +----------------
> > +While launching a guest with vIOMMU, it is strongly advised to check
> > +the compatibility upfront, as some subsequent errors happening during
> > +vIOMMU operation, such as cache invalidation failures cannot be
> > nicely> +escaladated to the guest due to IOMMU specifications. This can
> > nicely> lead to  
> 
>    escalated
> 
got it

> > +catastrophic failures for the users.
> > +
> > +User applications such as QEMU are expected to import kernel UAPI
> > +headers. Backward compatibility is supported per feature flags.
> > +For example, an older QEMU (with older kernel header) can run on newer
> > +kernel. Newer QEMU (with new kernel header) may refuse to initialize
> > +on an older kernel if new feature flags are not supported by older
> > +kernel. Simply recompiling existing code with newer kernel header
> > should +not be an issue in that only existing flags are used.
> > +
> > +IOMMU vendor driver should report the below features to IOMMU UAPI
> > +consumers (e.g. via VFIO).
> > +
> > +1. IOMMU_NESTING_FEAT_SYSWIDE_PASID
> > +2. IOMMU_NESTING_FEAT_BIND_PGTBL
> > +3. IOMMU_NESTING_FEAT_BIND_PASID_TABLE
> > +4. IOMMU_NESTING_FEAT_CACHE_INVLD
> > +5. IOMMU_NESTING_FEAT_PAGE_REQUEST
> > +
> > +Take VFIO as example, upon request from VFIO user space (e.g. QEMU),  
> 
>                                                 userspace
> 
> > +VFIO kernel code shall query IOMMU vendor driver for the support of
> > +the above features. Query result can then be reported back to the
> > +user-space caller. Details can be found in  
> 
>    userspace
> 
ditto

> > +Documentation/driver-api/vfio.rst.
> > +
> > +
> > +Data Passing Example with VFIO
> > +------------------------------
> > +As the ubiquitous userspace driver framework, VFIO is already IOMMU
> > +aware and shares many key concepts such as device model, group, and
> > +protection domain. Other user driver frameworks can also be extended
> > +to support IOMMU UAPI but it is outside the scope of this document.
> > +
> > +In this tight-knit VFIO-IOMMU interface, the ultimate consumer of the
> > +IOMMU UAPI data is the host IOMMU driver. VFIO facilitates user-kernel
> > +transport, capability checking, security, and life cycle management of
> > +process address space ID (PASID).
> > +
> > +VFIO layer conveys the data structures down to the IOMMU driver, it  
> 
>                                                             driver. It
> 
got it.

> > +follows the pattern below::
> > +
> > +   struct {
> > +	__u32 argsz;
> > +	__u32 flags;
> > +	__u8  data[];
> > +   };
> > +
> > +Here data[] contains the IOMMU UAPI data structures. VFIO has the
> > +freedom to bundle the data as well as parse data size based on its own
> > flags. +
> > +In order to determine the size and feature set of the user data, argsz
> > +and flags (or the equivalent) are also embedded in the IOMMU UAPI data
> > +structures.
> > +
> > +A "__u32 argsz" field is *always* at the beginning of each structure.
> > +
> > +For example:
> > +::
> > +
> > +   struct iommu_cache_invalidate_info {
> > +	__u32	argsz;
> > +	#define IOMMU_CACHE_INVALIDATE_INFO_VERSION_1 1
> > +	__u32	version;
> > +	/* IOMMU paging structure cache */
> > +	#define IOMMU_CACHE_INV_TYPE_IOTLB	(1 << 0) /* IOMMU
> > IOTLB */
> > +	#define IOMMU_CACHE_INV_TYPE_DEV_IOTLB	(1 << 1) /*
> > Device IOTLB */
> > +	#define IOMMU_CACHE_INV_TYPE_PASID	(1 << 2) /* PASID
> > cache */
> > +	#define IOMMU_CACHE_INV_TYPE_NR		(3)
> > +	__u8	cache;
> > +	__u8	granularity;
> > +	__u8	padding[6];
> > +	union {
> > +		struct iommu_inv_pasid_info pasid_info;
> > +		struct iommu_inv_addr_info addr_info;
> > +	} granu;
> > +   };
> > +
> > +VFIO is responsible for checking its own argsz and flags. It then
> > +invokes appropriate IOMMU UAPI functions. The user pointers are passed
> > +to the IOMMU layer for further processing. The responsibilities are
> > +divided as follows:
> > +
> > +- Generic IOMMU layer checks argsz range based on UAPI data in the
> > +  current kernel version  
> 
>                     version.
> 
got it

> > +
> > +- Generic IOMMU layer checks content of the UAPI data for non-zero
> > +  reserved bits in flags, padding fields, and unsupported version.
> > +  This is to ensure not breaking userspace in the future when these
> > +  fields or flags are used.
> > +
> > +- Vendor IOMMU driver checks argsz based on vendor flags, UAPI data  
> 
>                                                       flags. UAPI data
> 
got it

> > +  is consumed based on flags. Vendor driver has access to
> > +  unadulterated argsz value in case of vendor specific future
> > +  extensions. Currently, it does not perform the copy_from_user()
> > +  itself. A __user pointer can be provided in some future scenarios
> > +  where there's vendor data outside of the structure definition.
> > +
> > +IOMMU code treats UAPI data into two categories:  
> 
>                                 in
> 
got it

> > +
> > +- structure contains vendor data
> > +  (Example: iommu_uapi_cache_invalidate())
> > +
> > +- structure contains only generic data
> > +  (Example: iommu_uapi_sva_bind_gpasid())
> > +
> > +
> > +
> > +Sharing UAPI with in-kernel users
> > +---------------------------------
> > +For UAPIs that are shared with in-kernel users, a wrapper function is
> > +provided to distinguish the callers. For example,
> > +
> > +Userspace caller ::
> > +
> > +  int iommu_uapi_sva_unbind_gpasid(struct iommu_domain *domain,
> > +                                   struct device *dev,
> > +                                   void __user *udata)
> > +
> > +In-kernel caller ::
> > +
> > +  int iommu_sva_unbind_gpasid(struct iommu_domain *domain,
> > +                                   struct device *dev,
> > +                                   struct iommu_gpasid_bind_data
> > *data)  
> 
> 
> thanks.


Thanks,

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

^ permalink raw reply	[flat|nested] 17+ messages in thread

* Re: [PATCH v9 3/7] iommu/uapi: Introduce enum type for PASID data format
  2020-09-18 17:11     ` Jacob Pan
@ 2020-09-22 20:24       ` Jacob Pan
  2020-09-24  8:40       ` Joerg Roedel
  1 sibling, 0 replies; 17+ messages in thread
From: Jacob Pan @ 2020-09-22 20:24 UTC (permalink / raw)
  To: Joerg Roedel
  Cc: Tian, Kevin, Jacob Pan, Raj Ashok, Jonathan Corbet,
	Jean-Philippe Brucker, iommu, LKML, Alex Williamson, Wu Hao,
	David Woodhouse, Yi Sun

Hi Joerg,

I sent out v10 with Randy's comments addressed but I didn't change this
patch. Does my explanation below make sense? I am hoping to make it in
v5.10 since many other pieces depend on it, your guidance is much
appreciated.

Jacob


On Fri, 18 Sep 2020 10:11:08 -0700, Jacob Pan
<jacob.jun.pan@linux.intel.com> wrote:

> Hi Joerg,
> 
> On Fri, 18 Sep 2020 11:44:50 +0200, Joerg Roedel <joro@8bytes.org> wrote:
> 
> > On Fri, Sep 11, 2020 at 02:57:52PM -0700, Jacob Pan wrote:  
> > > There can be multiple vendor-specific PASID data formats used in UAPI
> > > structures. This patch adds enum type with a last entry which makes
> > > range checking much easier.    
> > 
> > But it also makes it much easier to screw up the numbers (which are ABI)
> > by inserting a new value into the middle. I prefer defines here, or
> > alternativly BUILD_BUG_ON() checks for the numbers.
> >   
> I am not following, the purpose of IOMMU_PASID_FORMAT_LAST *is* for
> preparing the future insertion of new value into the middle.
> The checking against IOMMU_PASID_FORMAT_LAST is to protect ABI
> compatibility by making sure that out of range format are rejected in all
> versions of the ABI.
> For example, in v5.10, ABI has IOMMU_PASID_FORMAT_LAST = 2, then user data
> with format = 2 will be rejected. So this user app will not work or
> released.
> 
> Now say in v5.11, we add one more format in the middle and set
> IOMMU_PASID_FORMAT_LAST = 3. Then user data with the new format = 2 can
> be supported.
> 
> Without the checking for IOMMU_PASID_FORMAT_LAST, at v5.10 time the user
> binary may succeed and become legacy binary that we cannot break in v5.11.
> This renders format = 2 unusable for v5.11.
> 
> I thought enum makes it less susceptible to programming errors than
> defines by making sure the ascending order. I might have missed your
> point, could you elaborate?
> 
> > Regards,
> > 
> > 	Joerg
> >   
> > > 
> > > Suggested-by: Alex Williamson <alex.williamson@redhat.com>
> > > Reviewed-by: Eric Auger <eric.auger@redhat.com>
> > > Signed-off-by: Jacob Pan <jacob.jun.pan@linux.intel.com>
> > > ---
> > >  include/uapi/linux/iommu.h | 8 ++++++--
> > >  1 file changed, 6 insertions(+), 2 deletions(-)
> > > 
> > > diff --git a/include/uapi/linux/iommu.h b/include/uapi/linux/iommu.h
> > > index b42acc8fe007..7cc6ee6c41f7 100644
> > > --- a/include/uapi/linux/iommu.h
> > > +++ b/include/uapi/linux/iommu.h
> > > @@ -298,11 +298,16 @@ struct iommu_gpasid_bind_data_vtd {
> > >  					 IOMMU_SVA_VTD_GPASID_PCD |
> > > \ IOMMU_SVA_VTD_GPASID_PWT)
> > >  
> > > +enum iommu_pasid_data_format {
> > > +	IOMMU_PASID_FORMAT_INTEL_VTD = 1,
> > > +	IOMMU_PASID_FORMAT_LAST,
> > > +};
> > > +
> > >  /**
> > >   * 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
> > > + * @format:	PASID table entry format of enum
> > > iommu_pasid_data_format type
> > >   * @flags:	Additional information on guest bind request
> > >   * @gpgd:	Guest page directory base of the guest mm to bind
> > >   * @hpasid:	Process address space ID used for the guest mm in
> > > host IOMMU @@ -321,7 +326,6 @@ struct iommu_gpasid_bind_data {
> > >  	__u32 argsz;
> > >  #define IOMMU_GPASID_BIND_VERSION_1	1
> > >  	__u32 version;
> > > -#define IOMMU_PASID_FORMAT_INTEL_VTD	1
> > >  	__u32 format;
> > >  	__u32 addr_width;
> > >  #define IOMMU_SVA_GPASID_VAL	(1 << 0) /* guest PASID valid */
> > > -- 
> > > 2.7.4    
> 
> 
> Thanks,
> 
> Jacob


Thanks,

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

^ permalink raw reply	[flat|nested] 17+ messages in thread

* Re: [PATCH v9 3/7] iommu/uapi: Introduce enum type for PASID data format
  2020-09-18 17:11     ` Jacob Pan
  2020-09-22 20:24       ` Jacob Pan
@ 2020-09-24  8:40       ` Joerg Roedel
  2020-09-24 18:31         ` Jacob Pan
  1 sibling, 1 reply; 17+ messages in thread
From: Joerg Roedel @ 2020-09-24  8:40 UTC (permalink / raw)
  To: Jacob Pan
  Cc: Tian, Kevin, Jacob Pan, Raj Ashok, Jonathan Corbet,
	Jean-Philippe Brucker, iommu, LKML, Alex Williamson, Wu Hao,
	David Woodhouse, Yi Sun

Hi Jacob,

On Fri, Sep 18, 2020 at 10:11:08AM -0700, Jacob Pan wrote:
> On Fri, 18 Sep 2020 11:44:50 +0200, Joerg Roedel <joro@8bytes.org> wrote:
> 
> > On Fri, Sep 11, 2020 at 02:57:52PM -0700, Jacob Pan wrote:
> > > There can be multiple vendor-specific PASID data formats used in UAPI
> > > structures. This patch adds enum type with a last entry which makes
> > > range checking much easier.  
> > 
> > But it also makes it much easier to screw up the numbers (which are ABI)
> > by inserting a new value into the middle. I prefer defines here, or
> > alternativly BUILD_BUG_ON() checks for the numbers.
> > 
> I am not following, the purpose of IOMMU_PASID_FORMAT_LAST *is* for
> preparing the future insertion of new value into the middle.
> The checking against IOMMU_PASID_FORMAT_LAST is to protect ABI
> compatibility by making sure that out of range format are rejected in all
> versions of the ABI.

But with the enum you could have:

enum {
	VTD_FOO,
	SMMU_FOO,
	LAST,
};

which makes VTD_FOO==0 and SMMU_FOO==1, and when in the next version
someone adds:

enum {
	VTD_FOO,
	VTD_BAR,
	SMMU_FOO,
	LAST,
};

then SMMU_FOO will become 2 and break ABI. So I'd like to have this
checked somewhere.

Regards,

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

^ permalink raw reply	[flat|nested] 17+ messages in thread

* Re: [PATCH v9 3/7] iommu/uapi: Introduce enum type for PASID data format
  2020-09-24  8:40       ` Joerg Roedel
@ 2020-09-24 18:31         ` Jacob Pan
  0 siblings, 0 replies; 17+ messages in thread
From: Jacob Pan @ 2020-09-24 18:31 UTC (permalink / raw)
  To: Joerg Roedel
  Cc: Tian, Kevin, Jacob Pan, Raj Ashok, Jonathan Corbet,
	Jean-Philippe Brucker, iommu, LKML, Alex Williamson, Wu Hao,
	David Woodhouse, Yi Sun

Hi Joerg,

On Thu, 24 Sep 2020 10:40:16 +0200, Joerg Roedel <joro@8bytes.org> wrote:

> > On Fri, 18 Sep 2020 11:44:50 +0200, Joerg Roedel <joro@8bytes.org>
> > wrote: 
> > > On Fri, Sep 11, 2020 at 02:57:52PM -0700, Jacob Pan wrote:  
> > > > There can be multiple vendor-specific PASID data formats used in
> > > > UAPI structures. This patch adds enum type with a last entry which
> > > > makes range checking much easier.    
> > > 
> > > But it also makes it much easier to screw up the numbers (which are
> > > ABI) by inserting a new value into the middle. I prefer defines here,
> > > or alternativly BUILD_BUG_ON() checks for the numbers.
> > >   
> > I am not following, the purpose of IOMMU_PASID_FORMAT_LAST *is* for
> > preparing the future insertion of new value into the middle.
> > The checking against IOMMU_PASID_FORMAT_LAST is to protect ABI
> > compatibility by making sure that out of range format are rejected in
> > all versions of the ABI.  
> 
> But with the enum you could have:
> 
> enum {
> 	VTD_FOO,
> 	SMMU_FOO,
> 	LAST,
> };
> 
> which makes VTD_FOO==0 and SMMU_FOO==1, and when in the next version
> someone adds:
> 
> enum {
> 	VTD_FOO,
> 	VTD_BAR,
> 	SMMU_FOO,
> 	LAST,
> };
> 
> then SMMU_FOO will become 2 and break ABI. So I'd like to have this
> checked somewhere.
Got your point, will change to defines.

Thanks,

Jacob
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^ permalink raw reply	[flat|nested] 17+ messages in thread

end of thread, other threads:[~2020-09-24 18:29 UTC | newest]

Thread overview: 17+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2020-09-11 21:57 [PATCH v9 0/7] IOMMU user API enhancement Jacob Pan
2020-09-11 21:57 ` [PATCH v9 1/7] docs: IOMMU user API Jacob Pan
2020-09-16 18:26   ` Randy Dunlap
2020-09-18 19:44     ` Jacob Pan
2020-09-11 21:57 ` [PATCH v9 2/7] iommu/uapi: Add argsz for user filled data Jacob Pan
2020-09-11 21:57 ` [PATCH v9 3/7] iommu/uapi: Introduce enum type for PASID data format Jacob Pan
2020-09-18  9:44   ` Joerg Roedel
2020-09-18 17:11     ` Jacob Pan
2020-09-22 20:24       ` Jacob Pan
2020-09-24  8:40       ` Joerg Roedel
2020-09-24 18:31         ` Jacob Pan
2020-09-11 21:57 ` [PATCH v9 4/7] iommu/uapi: Use named union for user data Jacob Pan
2020-09-11 21:57 ` [PATCH v9 5/7] iommu/uapi: Rename uapi functions Jacob Pan
2020-09-11 21:57 ` [PATCH v9 6/7] iommu/uapi: Handle data and argsz filled by users Jacob Pan
2020-09-11 21:57 ` [PATCH v9 7/7] iommu/vt-d: Check UAPI data processed by IOMMU core Jacob Pan
2020-09-18 10:02 ` [PATCH v9 0/7] IOMMU user API enhancement Joerg Roedel
2020-09-18 17:26   ` Jacob Pan

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