This series implements the functionality of delivering IO page faults to user space through the IOMMUFD framework. One feasible use case is the nested translation. Nested translation is a hardware feature that supports two-stage translation tables for IOMMU. The second-stage translation table is managed by the host VMM, while the first-stage translation table is owned by user space. This allows user space to control the IOMMU mappings for its devices. When an IO page fault occurs on the first-stage translation table, the IOMMU hardware can deliver the page fault to user space through the IOMMUFD framework. User space can then handle the page fault and respond to the device top-down through the IOMMUFD. This allows user space to implement its own IO page fault handling policies. User space application that is capable of handling IO page faults should allocate a fault object, and bind the fault object to any domain that it is willing to handle the fault generatd for them. On a successful return of fault object allocation, the user can retrieve and respond to page faults by reading or writing to the file descriptor (FD) returned. The iommu selftest framework has been updated to test the IO page fault delivery and response functionality. The series and related patches are available on GitHub: https://github.com/LuBaolu/intel-iommu/commits/iommufd-io-pgfault-delivery-v4 Change log: v4: - Add the iommu domain attachment handle to replace the iopf-specific domain attachment interfaces introduced in the previous v3. - Replace the iommu_sva with iommu domain attachment handle. - Refine some fields in the fault and response message encoding according to feedback collected during v3 review period. - Refine and fix some problems in the fault FD implementation. - Miscellaneous cleanup. v3: https://lore.kernel.org/linux-iommu/20240122073903.24406-1-baolu.lu@xxxxxxxxxxxxxxx/ - Add iopf domain attach/detach/replace interfaces to manage the reference counters of hwpt and device, ensuring that both can only be destroyed after all outstanding IOPFs have been responded to. - Relocate the fault handling file descriptor from hwpt to a fault object to enable a single fault handling object to be utilized across multiple domains. - Miscellaneous cleanup and performance improvements. v2: https://lore.kernel.org/linux-iommu/20231026024930.382898-1-baolu.lu@xxxxxxxxxxxxxxx/ - Move all iommu refactoring patches into a sparated series and discuss it in a different thread. The latest patch series [v6] is available at https://lore.kernel.org/linux-iommu/20230928042734.16134-1-baolu.lu@xxxxxxxxxxxxxxx/ - We discussed the timeout of the pending page fault messages. We agreed that we shouldn't apply any timeout policy for the page fault handling in user space. https://lore.kernel.org/linux-iommu/20230616113232.GA84678@myrica/ - Jason suggested that we adopt a simple file descriptor interface for reading and responding to I/O page requests, so that user space applications can improve performance using io_uring. https://lore.kernel.org/linux-iommu/ZJWjD1ajeem6pK3I@xxxxxxxx/ v1: https://lore.kernel.org/linux-iommu/20230530053724.232765-1-baolu.lu@xxxxxxxxxxxxxxx/ Lu Baolu (9): iommu: Introduce domain attachment handle iommu: Replace sva_iommu with iommu_attach_handle iommu: Add attachment handle to struct iopf_group iommufd: Fault-capable hw page table attach/detach/replace iommufd: Add fault and response message definitions iommufd: Add iommufd fault object iommufd: Associate fault object with iommufd_hw_pgtable iommufd/selftest: Add IOPF support for mock device iommufd/selftest: Add coverage for IOPF test include/linux/iommu.h | 33 +- include/linux/uacce.h | 2 +- drivers/dma/idxd/idxd.h | 2 +- drivers/iommu/iommu-priv.h | 9 + drivers/iommu/iommufd/iommufd_private.h | 43 ++ drivers/iommu/iommufd/iommufd_test.h | 8 + include/uapi/linux/iommufd.h | 122 ++++++ tools/testing/selftests/iommu/iommufd_utils.h | 84 +++- drivers/dma/idxd/cdev.c | 4 +- drivers/iommu/io-pgfault.c | 37 +- drivers/iommu/iommu-sva.c | 64 ++- drivers/iommu/iommu.c | 158 +++++++- drivers/iommu/iommufd/device.c | 16 +- drivers/iommu/iommufd/fault.c | 372 ++++++++++++++++++ drivers/iommu/iommufd/hw_pagetable.c | 36 +- drivers/iommu/iommufd/main.c | 6 + drivers/iommu/iommufd/selftest.c | 63 +++ drivers/misc/uacce/uacce.c | 2 +- tools/testing/selftests/iommu/iommufd.c | 18 + .../selftests/iommu/iommufd_fail_nth.c | 2 +- drivers/iommu/iommufd/Makefile | 1 + 21 files changed, 968 insertions(+), 114 deletions(-) create mode 100644 drivers/iommu/iommufd/fault.c -- 2.34.1
