With the introduction of the new object and its infrastructure, update the doc to reflect that and add a new graph.
Signed-off-by: Nicolin Chen nicolinc@nvidia.com --- Documentation/userspace-api/iommufd.rst | 66 ++++++++++++++++++++++++- 1 file changed, 65 insertions(+), 1 deletion(-)
diff --git a/Documentation/userspace-api/iommufd.rst b/Documentation/userspace-api/iommufd.rst index 2deba93bf159..37eb1adda57b 100644 --- a/Documentation/userspace-api/iommufd.rst +++ b/Documentation/userspace-api/iommufd.rst @@ -63,6 +63,37 @@ Following IOMMUFD objects are exposed to userspace: space usually has mappings from guest-level I/O virtual addresses to guest- level physical addresses.
+ - 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: + * Security namespace for guest owned ID, e.g. guest-controlled cache tags + * Access to a sharable nesting parent pagetable across physical IOMMUs + * Virtualization of various platforms IDs, e.g. RIDs and others + * Delivery of paravirtualized invalidation + * Direct assigned invalidation queues + * Direct assigned interrupts + * Non-affiliated event reporting + Such a vIOMMU object generally has the access to a nesting parent pagetable + to support some HW-accelerated virtualization features. So, a vIOMMU object + must be created given a nesting parent HWPT_PAGING object, and then it would + encapsulate that HWPT_PAGING object. Therefore, a vIOMMU object can be used + to allocate an HWPT_NESTED object in place of the encapsulated HWPT_PAGING. + + .. note:: + + The name "vIOMMU" isn't necessarily identical to a virtualized IOMMU in a + VM. A VM can have one giant virtualized IOMMU running on a machine having + multiple physical IOMMUs, in which case the VMM will dispatch the requests + or configurations from this single virtualized IOMMU instance to multiple + vIOMMU objects created for individual slices of different physical IOMMUs. + In other words, a vIOMMU object is always a representation of one physical + IOMMU, not necessarily of a virtualized IOMMU. For VMMs that want the full + virtualization features from physical IOMMUs, it is suggested to build the + same number of virtualized IOMMUs as the number of physical IOMMUs, so the + passed-through devices would be connected to their own virtualized IOMMUs + backed by corresponding vIOMMU objects, in which case a guest OS would do + the "dispatch" naturally instead of VMM trappings. + All user-visible objects are destroyed via the IOMMU_DESTROY uAPI.
The diagrams below show relationships between user-visible objects and kernel @@ -101,6 +132,25 @@ creating the objects and links:: |------------>|iommu_domain|<----|iommu_domain|<----|device| |____________| |____________| |______|
+ _______________________________________________________________________ + | iommufd (with vIOMMU) | + | | + | [5] | + | _____________ | + | | | | + | [1] | vIOMMU | [4] [2] | + | ________________ | | _____________ ________ | + | | | | [3] | | | | | | + | | IOAS |<---|(HWPT_PAGING)|<---| HWPT_NESTED |<--| DEVICE | | + | |________________| |_____________| |_____________| |________| | + | | | | | | + |_________|____________________|__________________|_______________|_____| + | | | | + | ______v_____ ______v_____ ___v__ + | PFN storage | (paging) | | (nested) | |struct| + |------------>|iommu_domain|<----|iommu_domain|<----|device| + |____________| |____________| |______| + 1. IOMMUFD_OBJ_IOAS is created via the IOMMU_IOAS_ALLOC uAPI. An iommufd can hold multiple IOAS objects. IOAS is the most generic object and does not expose interfaces that are specific to single IOMMU drivers. All operations @@ -132,7 +182,8 @@ creating the objects and links:: flag is set.
4. IOMMUFD_OBJ_HWPT_NESTED can be only manually created via the IOMMU_HWPT_ALLOC - uAPI, provided an hwpt_id via @pt_id to associate the new HWPT_NESTED object + uAPI, provided an hwpt_id or a viommu_id of a vIOMMU object encapsulating a + nesting parent HWPT_PAGING via @pt_id to associate the new HWPT_NESTED object to the corresponding HWPT_PAGING object. The associating HWPT_PAGING object must be a nesting parent manually allocated via the same uAPI previously with an IOMMU_HWPT_ALLOC_NEST_PARENT flag, otherwise the allocation will fail. The @@ -149,6 +200,18 @@ creating the objects and links:: created via the same IOMMU_HWPT_ALLOC uAPI. The difference is at the type of the object passed in via the @pt_id field of struct iommufd_hwpt_alloc.
+5. IOMMUFD_OBJ_VIOMMU can be only manually created via the IOMMU_VIOMMU_ALLOC + uAPI, provided a dev_id (for the device's physical IOMMU to back the vIOMMU) + and an hwpt_id (to associate the vIOMMU to a nesting parent HWPT_PAGING). The + iommufd core will link the vIOMMU object to the struct iommu_device that the + struct device is behind. And an IOMMU driver can implement a viommu_alloc op + to allocate its own vIOMMU data structure embedding the core-level structure + iommufd_viommu and some driver-specific data. If necessary, the driver can + also configure its HW virtualization feature for that vIOMMU (and thus for + the VM). Successful completion of this operation sets up the linkages between + 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. + 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).
@@ -161,6 +224,7 @@ 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_viommu for IOMMUFD_OBJ_VIOMMU.
Several terminologies when looking at these datastructures: