[PATCH v7 11/14] Documentation: userspace-api: iommufd: Update FAULT and VEVENTQ

Nicolin Chen
2025-02-22T15:54:50Z

With the introduction of the new objects, update the doc to reflect that.

Reviewed-by: Lu Baolu <baolu.lu@linux.intel.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Reviewed-by: Bagas Sanjaya <bagasdotme@gmail.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Signed-off-by: Nicolin Chen <nicolinc@nvidia.com>
---
Documentation/userspace-api/iommufd.rst | 17 +++++++++++++++++
1 file changed, 17 insertions(+)

diff --git a/Documentation/userspace-api/iommufd.rst b/Documentation/userspace-api/iommufd.rst
index 70289d6815d2..b0df15865dec 100644
--- a/Documentation/userspace-api/iommufd.rst
+++ b/Documentation/userspace-api/iommufd.rst
@@ -63,6 +63,13 @@ Following IOMMUFD objects are exposed to userspace:
space usually has mappings from guest-level I/O virtual addresses to guest-
level physical addresses.

+- IOMMUFD_FAULT, representing a software queue for an HWPT reporting IO page
+ faults using the IOMMU HW's PRI (Page Request Interface). This queue object
+ provides user space an FD to poll the page fault events and also to respond
+ to those events. A FAULT object must be created first to get a fault_id that
+ could be then used to allocate a fault-enabled HWPT via the IOMMU_HWPT_ALLOC
+ command by setting the IOMMU_HWPT_FAULT_ID_VALID bit in its flags field.
+
- IOMMUFD_OBJ_VIOMMU, representing a slice of the physical IOMMU instance,
passed to or shared with a VM. It may be some HW-accelerated virtualization
features and some SW resources used by the VM. For examples:
@@ -109,6 +116,14 @@ Following IOMMUFD objects are exposed to userspace:
vIOMMU, which is a separate ioctl call from attaching the same device to an
HWPT_PAGING that the vIOMMU holds.

+- IOMMUFD_OBJ_VEVENTQ, representing a software queue for a vIOMMU to report its
+ events such as translation faults occurred to a nested stage-1 (excluding I/O
+ page faults that should go through IOMMUFD_OBJ_FAULT) and HW-specific events.
+ This queue object provides user space an FD to poll/read the vIOMMU events. A
+ vIOMMU object must be created first to get its viommu_id, which could be then
+ used to allocate a vEVENTQ. Each vIOMMU can support multiple types of vEVENTS,
+ but is confined to one vEVENTQ per vEVENTQ type.
+
All user-visible objects are destroyed via the IOMMU_DESTROY uAPI.

The diagrams below show relationships between user-visible objects and kernel
@@ -251,8 +266,10 @@ User visible objects are backed by following datastructures:
- iommufd_device for IOMMUFD_OBJ_DEVICE.
- iommufd_hwpt_paging for IOMMUFD_OBJ_HWPT_PAGING.
- iommufd_hwpt_nested for IOMMUFD_OBJ_HWPT_NESTED.
+- iommufd_fault for IOMMUFD_OBJ_FAULT.
- iommufd_viommu for IOMMUFD_OBJ_VIOMMU.
- iommufd_vdevice for IOMMUFD_OBJ_VDEVICE.
+- iommufd_veventq for IOMMUFD_OBJ_VEVENTQ.

Several terminologies when looking at these datastructures:

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2.43.0