[PATCH v2 2/6] iommufd: Add iommu page fault uapi data

[Lu Baolu]

For user to handle IO page faults generated by IOMMU hardware when
walking the HWPT managed by the user. One example of the use case
is nested translation, where the first-stage page table is managed
by the user space.

When allocating a user HWPT, the user could opt-in a flag named
IOMMU_HWPT_ALLOC_IOPF_CAPABLE, which indicates that user is capable
of handling IO page faults generated for this HWPT.

On a successful return of hwpt allocation, the user can retrieve
and respond the page faults by reading and writing the fd returned
in out_fault_fd. The format of the page fault and response data is
encoded in the format defined by struct iommu_hwpt_pgfault and
struct iommu_hwpt_response.

The iommu_hwpt_pgfault is mostly like the iommu_fault with some new
members like fault data size and the device object id where the page
fault was originated from.

Signed-off-by: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>
---
 include/uapi/linux/iommufd.h | 65 ++++++++++++++++++++++++++++++++++++
 1 file changed, 65 insertions(+)

diff --git a/include/uapi/linux/iommufd.h b/include/uapi/linux/iommufd.h
index f9b8b95b36b2..0f00f1dfcded 100644
--- a/include/uapi/linux/iommufd.h
+++ b/include/uapi/linux/iommufd.h
@@ -355,9 +355,17 @@ struct iommu_vfio_ioas {
  * @IOMMU_HWPT_ALLOC_NEST_PARENT: If set, allocate a domain which can serve
  *                                as the parent domain in the nesting
  *                                configuration.
+ * @IOMMU_HWPT_ALLOC_IOPF_CAPABLE: User is capable of handling IO page faults.
+ *                                 On successful return, user can retrieve
+ *                                 faults by reading the @out_fault_fd and
+ *                                 respond the faults by writing it. The fault
+ *                                 data is encoded in the format defined by
+ *                                 iommu_hwpt_pgfault. The response data format
+ *                                 is defined by iommu_hwpt_page_response
  */
 enum iommufd_hwpt_alloc_flags {
 	IOMMU_HWPT_ALLOC_NEST_PARENT = 1 << 0,
+	IOMMU_HWPT_ALLOC_IOPF_CAPABLE = 1 << 1,
 };
 
 /**
@@ -476,6 +484,7 @@ struct iommu_hwpt_alloc {
 	__u32 hwpt_type;
 	__u32 data_len;
 	__aligned_u64 data_uptr;
+	__u32 out_fault_fd;
 };
 #define IOMMU_HWPT_ALLOC _IO(IOMMUFD_TYPE, IOMMUFD_CMD_HWPT_ALLOC)
 
@@ -679,6 +688,62 @@ struct iommu_dev_data_arm_smmuv3 {
 	__u32 sid;
 };
 
+/**
+ * struct iommu_hwpt_pgfault - iommu page fault data
+ * @size: sizeof(struct iommu_hwpt_pgfault)
+ * @flags: Combination of IOMMU_PGFAULT_FLAGS_ flags.
+ *  - PASID_VALID: @pasid field is valid
+ *  - LAST_PAGE: the last page fault in a group
+ *  - PRIV_DATA: @private_data field is valid
+ *  - RESP_NEEDS_PASID: the page response must have the same
+ *                      PASID value as the page request.
+ * @dev_id: id of the originated device
+ * @pasid: Process Address Space ID
+ * @grpid: Page Request Group Index
+ * @perm: requested page permissions (IOMMU_PGFAULT_PERM_* values)
+ * @addr: page address
+ * @private_data: device-specific private information
+ */
+struct iommu_hwpt_pgfault {
+	__u32 size;
+	__u32 flags;
+#define IOMMU_PGFAULT_FLAGS_PASID_VALID		(1 << 0)
+#define IOMMU_PGFAULT_FLAGS_LAST_PAGE		(1 << 1)
+#define IOMMU_PGFAULT_FLAGS_PRIV_DATA		(1 << 2)
+#define IOMMU_PGFAULT_FLAGS_RESP_NEEDS_PASID	(1 << 3)
+	__u32 dev_id;
+	__u32 pasid;
+	__u32 grpid;
+	__u32 perm;
+#define IOMMU_PGFAULT_PERM_READ			(1 << 0)
+#define IOMMU_PGFAULT_PERM_WRITE		(1 << 1)
+#define IOMMU_PGFAULT_PERM_EXEC			(1 << 2)
+#define IOMMU_PGFAULT_PERM_PRIV			(1 << 3)
+	__u64 addr;
+	__u64 private_data[2];
+};
+
+/**
+ * struct iommu_hwpt_response - IOMMU page fault response
+ * @size: sizeof(struct iommu_hwpt_response)
+ * @flags: Must be set to 0
+ * @hwpt_id: hwpt ID of target hardware page table for the response
+ * @dev_id: device ID of target device for the response
+ * @pasid: Process Address Space ID
+ * @grpid: Page Request Group Index
+ * @code: response code. The supported codes include:
+ *        0: Successful; 1: Response Failure; 2: Invalid Request.
+ */
+struct iommu_hwpt_page_response {
+	__u32 size;
+	__u32 flags;
+	__u32 hwpt_id;
+	__u32 dev_id;
+	__u32 pasid;
+	__u32 grpid;
+	__u32 code;
+};
+
 /**
  * struct iommu_set_dev_data - ioctl(IOMMU_SET_DEV_DATA)
  * @size: sizeof(struct iommu_set_dev_data)
-- 
2.34.1