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Documentation: userspace-api: iommufd: Update vDEVICE

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With the introduction of the new object and its infrastructure, update the
doc and the vIOMMU graph to reflect that.

Link: https://patch.msgid.link/r/e1ff278b7163909b2641ae04ff364bb41d2a2a2e.1730836308.git.nicolinc@nvidia.com
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Signed-off-by: Nicolin Chen <nicolinc@nvidia.com>
Reviewed-by: Bagas Sanjaya <bagasdotme@gmail.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
This commit is contained in:
Nicolin Chen 2024-11-05 12:05:18 -08:00 committed by Jason Gunthorpe
parent 49ad127719
commit b047c0644f
1 changed files with 32 additions and 9 deletions
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41
Documentation/userspace-api/iommufd.rst
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@ -96,6 +96,19 @@ Following IOMMUFD objects are exposed to userspace:
backed by corresponding vIOMMU objects, in which case a guest OS would do
the "dispatch" naturally instead of VMM trappings.
- IOMMUFD_OBJ_VDEVICE, representing a virtual device for an IOMMUFD_OBJ_DEVICE
against an IOMMUFD_OBJ_VIOMMU. This virtual device holds the device's virtual
information or attributes (related to the vIOMMU) in a VM. An immediate vDATA
example can be the virtual ID of the device on a vIOMMU, which is a unique ID
that VMM assigns to the device for a translation channel/port of the vIOMMU,
e.g. vSID of ARM SMMUv3, vDeviceID of AMD IOMMU, and vRID of Intel VT-d to a
Context Table. Potential use cases of some advanced security information can
be forwarded via this object too, such as security level or realm information
in a Confidential Compute Architecture. A VMM should create a vDEVICE object
to forward all the device information in a VM, when it connects a device to a
vIOMMU, which is a separate ioctl call from attaching the same device to an
HWPT_PAGING that the vIOMMU holds.
All user-visible objects are destroyed via the IOMMU_DESTROY uAPI.
The diagrams below show relationships between user-visible objects and kernel
@ -135,16 +148,16 @@ creating the objects and links::
|____________| |____________| |______|
_______________________________________________________________________
| iommufd (with vIOMMU) |
| iommufd (with vIOMMU/vDEVICE) |
| |
| [5] |
| _____________ |
| | | |
| |----------------| vIOMMU | |
| | | | |
| | | | |
| | [1] | | [4] [2] |
| | ______ | | _____________ ________ |
| [5] [6] |
| _____________ _____________ |
| | | | | |
| |----------------| vIOMMU |<---| vDEVICE |<----| |
| | | | |_____________| | |
| | | | | |
| | [1] | | [4] | [2] |
| | ______ | | _____________ _|______ |
| | | | | [3] | | | | | |
| | | IOAS |<---|(HWPT_PAGING)|<---| HWPT_NESTED |<--| DEVICE | |
| | |______| |_____________| |_____________| |________| |
@ -217,6 +230,15 @@ creating the objects and links::
the vIOMMU object and the HWPT_PAGING, then this vIOMMU object can be used
as a nesting parent object to allocate an HWPT_NESTED object described above.
6. IOMMUFD_OBJ_VDEVICE can be only manually created via the IOMMU_VDEVICE_ALLOC
uAPI, provided a viommu_id for an iommufd_viommu object and a dev_id for an
iommufd_device object. The vDEVICE object will be the binding between these
two parent objects. Another @virt_id will be also set via the uAPI providing
the iommufd core an index to store the vDEVICE object to a vDEVICE array per
vIOMMU. If necessary, the IOMMU driver may choose to implement a vdevce_alloc
op to init its HW for virtualization feature related to a vDEVICE. Successful
completion of this operation sets up the linkages between vIOMMU and device.
A device can only bind to an iommufd due to DMA ownership claim and attach to at
most one IOAS object (no support of PASID yet).
@ -230,6 +252,7 @@ User visible objects are backed by following datastructures:
- iommufd_hwpt_paging for IOMMUFD_OBJ_HWPT_PAGING.
- iommufd_hwpt_nested for IOMMUFD_OBJ_HWPT_NESTED.
- iommufd_viommu for IOMMUFD_OBJ_VIOMMU.
- iommufd_vdevice for IOMMUFD_OBJ_VDEVICE.
Several terminologies when looking at these datastructures: