This series introduces a new vIOMMU infrastructure and related ioctls.
IOMMUFD has been using the HWPT infrastructure for all cases, including a nested IO page table support. Yet, there're limitations for an HWPT-based structure to support some advanced HW-accelerated features, such as CMDQV on NVIDIA Grace, and HW-accelerated vIOMMU on AMD. Even for a multi-IOMMU environment, it is not straightforward for nested HWPTs to share the same parent HWPT (stage-2 IO pagetable), with the HWPT infrastructure alone: a parent HWPT typically hold one stage-2 IO pagetable and tag it with only one ID in the cache entries. When sharing one large stage-2 IO pagetable across physical IOMMU instances, that one ID may not always be available across all the IOMMU instances. In other word, it's ideal for SW to have a different container for the stage-2 IO pagetable so it can hold another ID that's available.
For this "different container", add vIOMMU, an additional layer to hold extra virtualization information: _______________________________________________________________________ | 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| |____________| |____________| |______|
The vIOMMU object should be seen as a slice of a physical IOMMU instance that is passed to or shared with a VM. That can be some HW/SW resources: - 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
On a multi-IOMMU system, the vIOMMU object must be instanced to the number of the physical IOMMUs that are passed to (via devices) a guest VM, while being able to hold the shareable parent HWPT. Each vIOMMU then just needs to allocate its own individual ID to tag its own cache: ---------------------------- ---------------- | | paging_hwpt0 | | hwpt_nested0 |--->| viommu0 ------------------ ---------------- | | IDx | ---------------------------- ---------------------------- ---------------- | | paging_hwpt0 | | hwpt_nested1 |--->| viommu1 ------------------ ---------------- | | IDy | ----------------------------
As an initial part-1, add IOMMUFD_CMD_VIOMMU_ALLOC ioctl for an allocation only. Later series will add more data structures and their ioctls.
As for the implementation of the series, add an IOMMU_VIOMMU_TYPE_DEFAULT type for a core-allocated-core-managed vIOMMU object, allowing drivers to simply hook a default viommu ops for viommu-based invalidation alone. And add support for driver-specific type of vIOMMU allocation, and implement that in the ARM SMMUv3 driver for a real world use case.
More vIOMMU-based structs and ioctls will be introduced in the follow-up series to support vDEVICE, vIRQ (vEVENT) and VQUEUE objects. Although we repurposed the vIOMMU object from an earlier RFC, just for a referece: https://lore.kernel.org/all/cover.1712978212.git.nicolinc@nvidia.com/
This series is on Github: https://github.com/nicolinc/iommufd/commits/iommufd_viommu_p1-v3 (paring QEMU branch for testing will be provided with the part2 series)
Changelog v3 * Rebased on top of Jason's nesting v3 series https://lore.kernel.org/all/0-v3-e2e16cd7467f+2a6a1-smmuv3_nesting_jgg@nvidi... * Split the series into smaller parts * Added Jason's Reviewed-by * Added back viommu->iommu_dev * Added support for driver-allocated vIOMMU v.s. core-allocated * Dropped arm_smmu_cache_invalidate_user * Added an iommufd_test_wait_for_users() in selftest * Reworked test code to make viommu an individual FIXTURE * Added missing TEST_LENGTH case for the new ioctl command v2 https://lore.kernel.org/all/cover.1724776335.git.nicolinc@nvidia.com/ * Limited vdev_id to one per idev * Added a rw_sem to protect the vdev_id list * Reworked driver-level APIs with proper lockings * Added a new viommu_api file for IOMMUFD_DRIVER config * Dropped useless iommu_dev point from the viommu structure * Added missing index numnbers to new types in the uAPI header * Dropped IOMMU_VIOMMU_INVALIDATE uAPI; Instead, reuse the HWPT one * Reworked mock_viommu_cache_invalidate() using the new iommu helper * Reordered details of set/unset_vdev_id handlers for proper lockings v1 https://lore.kernel.org/all/cover.1723061377.git.nicolinc@nvidia.com/
Thanks! Nicolin
Nicolin Chen (11): iommufd: Move struct iommufd_object to public iommufd header iommufd: Rename _iommufd_object_alloc to iommufd_object_alloc_elm iommufd: Introduce IOMMUFD_OBJ_VIOMMU and its related struct iommufd/viommu: Add IOMMU_VIOMMU_ALLOC ioctl iommu: Pass in a viommu pointer to domain_alloc_user op iommufd: Allow pt_id to carry viommu_id for IOMMU_HWPT_ALLOC iommufd/selftest: Add refcount to mock_iommu_device iommufd/selftest: Add IOMMU_VIOMMU_TYPE_SELFTEST iommufd/selftest: Add IOMMU_VIOMMU_ALLOC test coverage Documentation: userspace-api: iommufd: Update vIOMMU iommu/arm-smmu-v3: Add IOMMU_VIOMMU_TYPE_ARM_SMMUV3 support
drivers/iommu/iommufd/Makefile | 5 +- drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h | 18 ++++ drivers/iommu/iommufd/iommufd_private.h | 23 ++--- drivers/iommu/iommufd/iommufd_test.h | 2 + include/linux/iommu.h | 15 +++ include/linux/iommufd.h | 52 +++++++++++ include/uapi/linux/iommufd.h | 54 +++++++++-- tools/testing/selftests/iommu/iommufd_utils.h | 28 ++++++ drivers/iommu/amd/iommu.c | 1 + .../arm/arm-smmu-v3/arm-smmu-v3-iommufd.c | 24 +++++ drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 2 + drivers/iommu/intel/iommu.c | 1 + drivers/iommu/iommufd/hw_pagetable.c | 27 +++++- drivers/iommu/iommufd/main.c | 38 ++------ drivers/iommu/iommufd/selftest.c | 79 ++++++++++++++-- drivers/iommu/iommufd/viommu.c | 91 +++++++++++++++++++ drivers/iommu/iommufd/viommu_api.c | 57 ++++++++++++ tools/testing/selftests/iommu/iommufd.c | 84 +++++++++++++++++ Documentation/userspace-api/iommufd.rst | 66 +++++++++++++- 19 files changed, 602 insertions(+), 65 deletions(-) create mode 100644 drivers/iommu/iommufd/viommu.c create mode 100644 drivers/iommu/iommufd/viommu_api.c