The vIOMMU object is designed to represent a slice of an IOMMU HW for its virtualization features shared with or passed to user space (a VM mostly) in a way of HW acceleration. This extended the HWPT-based design for more advanced virtualization feature.
HW QUEUE introduced by this series as a part of the vIOMMU infrastructure represents a HW accelerated queue/buffer for VM to use exclusively, e.g. - NVIDIA's Virtual Command Queue - AMD vIOMMU's Command Buffer, Event Log Buffer, and PPR Log Buffer each of which allows its IOMMU HW to directly access a queue memory owned by a guest VM and allows a guest OS to control the HW queue direclty, to avoid VM Exit overheads to improve the performance.
Introduce IOMMUFD_OBJ_HW_QUEUE and its pairing IOMMUFD_CMD_HW_QUEUE_ALLOC allowing VMM to forward the IOMMU-specific queue info, such as queue base address, size, and etc.
Meanwhile, a guest-owned queue needs the guest kernel to control the queue by reading/writing its consumer and producer indexes, via MMIO acceses to the hardware MMIO registers. Introduce an mmap infrastructure for iommufd to support passing through a piece of MMIO region from the host physical address space to the guest physical address space. The mmap info (offset/ length) used by an mmap syscall must be pre-allocated and returned to the user space via an output driver-data during an IOMMUFD_CMD_HW_QUEUE_ALLOC call. Thus, it requires a driver-specific user data support in the vIOMMU allocation flow.
As a real-world use case, this series implements a HW QUEUE support in the tegra241-cmdqv driver for VCMDQs on NVIDIA Grace CPU. In another word, it is also the Tegra CMDQV series Part-2 (user-space support), reworked from Previous RFCv1: https://lore.kernel.org/all/cover.1712978212.git.nicolinc@nvidia.com/ This enables the HW accelerated feature for NVIDIA Grace CPU. Compared to the standard SMMUv3 operating in the nested translation mode trapping CMDQ for TLBI and ATC_INV commands, this gives a huge performance improvement: 70% to 90% reductions of invalidation time were measured by various DMA unmap tests running in a guest OS.
// Unmap latencies from "dma_map_benchmark -g @granule -t @threads", // by toggling "/sys/kernel/debug/iommu/tegra241_cmdqv/bypass_vcmdq" @granule | @threads | bypass_vcmdq=1 | bypass_vcmdq=0 4KB 1 35.7 us 5.3 us 16KB 1 41.8 us 6.8 us 64KB 1 68.9 us 9.9 us 128KB 1 109.0 us 12.6 us 256KB 1 187.1 us 18.0 us 4KB 2 96.9 us 6.8 us 16KB 2 97.8 us 7.5 us 64KB 2 151.5 us 10.7 us 128KB 2 257.8 us 12.7 us 256KB 2 443.0 us 17.9 us
This is on Github: https://github.com/nicolinc/iommufd/commits/iommufd_hw_queue-v4
Paring QEMU branch for testing: https://github.com/nicolinc/qemu/commits/wip/for_iommufd_hw_queue-v4
Changelog v4 * Rebase on v6.15-rc5 * Add Reviewed-by from Vasant * Rename "vQUEUE" to "HW QUEUE" * Use "offset" and "length" for all mmap-related variables * [iommufd] Use u64 for guest PA * [iommufd] Fix typo in uAPI doc * [iommufd] Rename immap_id to offset * [iommufd] Drop the partial-size mmap support * [iommufd] Do not replace WARN_ON with WARN_ON_ONCE * [iommufd] Use "u64 base_addr" for queue base address * [iommufd] Use u64 base_pfn/num_pfns for immap structure * [iommufd] Correct the size passed in to mtree_alloc_range() * [iommufd] Add IOMMUFD_VIOMMU_FLAG_HW_QUEUE_READS_PA to viommu_ops v3 https://lore.kernel.org/all/cover.1746139811.git.nicolinc@nvidia.com/ * Add Reviewed-by from Baolu, Pranjal, and Alok * Revise kdocs, uAPI docs, and commit logs * Rename "vCMDQ" back to "vQUEUE" for AMD cases * [tegra] Add tegra241_vcmdq_hw_flush_timeout() * [tegra] Rename vsmmu_alloc to alloc_vintf_user * [tegra] Use writel for SID replacement registers * [tegra] Move mmap removal call to vsmmu_destroy op * [tegra] Fix revert in tegra241_vintf_alloc_lvcmdq_user() * [iommufd] Replace "& ~PAGE_MASK" with PAGE_ALIGNED() * [iommufd] Add an object-type "owner" to immap structure * [iommufd] Drop the ictx input in the new for-driver APIs * [iommufd] Add iommufd_vma_ops to keep track of mmap lifecycle * [iommufd] Add viommu-based iommufd_viommu_alloc/destroy_mmap helpers * [iommufd] Rename iommufd_ctx_alloc/free_mmap to _iommufd_alloc/destroy_mmap v2 https://lore.kernel.org/all/cover.1745646960.git.nicolinc@nvidia.com/ * Add Reviewed-by from Jason * [smmu] Fix vsmmu initial value * [smmu] Support impl for hw_info * [tegra] Rename "slot" to "vsid" * [tegra] Update kdocs and commit logs * [tegra] Map/unmap LVCMDQ dynamically * [tegra] Refcount the previous LVCMDQ * [tegra] Return -EEXIST if LVCMDQ exists * [tegra] Simplify VINTF cleanup routine * [tegra] Use vmid and s2_domain in vsmmu * [tegra] Rename "mmap_pgoff" to "immap_id" * [tegra] Add more addr and length validation * [iommufd] Add more narrative to mmap's kdoc * [iommufd] Add iommufd_struct_depend/undepend() * [iommufd] Rename vcmdq_free op to vcmdq_destroy * [iommufd] Fix bug in iommu_copy_struct_to_user() * [iommufd] Drop is_io from iommufd_ctx_alloc_mmap() * [iommufd] Test the queue memory for its contiguity * [iommufd] Return -ENXIO if address or length fails * [iommufd] Do not change @min_last in mock_viommu_alloc() * [iommufd] Generalize TEGRA241_VCMDQ data in core structure * [iommufd] Add selftest coverage for IOMMUFD_CMD_VCMDQ_ALLOC * [iommufd] Add iopt_pin_pages() to prevent queue memory from unmapping v1 https://lore.kernel.org/all/cover.1744353300.git.nicolinc@nvidia.com/
Thanks Nicolin
Nicolin Chen (23): iommufd/viommu: Add driver-allocated vDEVICE support iommu: Pass in a driver-level user data structure to viommu_alloc op iommufd/viommu: Allow driver-specific user data for a vIOMMU object iommu: Add iommu_copy_struct_to_user helper iommufd/driver: Let iommufd_viommu_alloc helper save ictx to viommu->ictx iommufd/driver: Add iommufd_struct_destroy to revert iommufd_viommu_alloc iommufd/selftest: Support user_data in mock_viommu_alloc iommufd/selftest: Add covearge for viommu data iommufd: Abstract iopt_pin_pages and iopt_unpin_pages helpers iommufd/viommu: Introduce IOMMUFD_OBJ_HW_QUEUE and its related struct iommufd/viommu: Add IOMMUFD_CMD_HW_QUEUE_ALLOC ioctl iommufd/driver: Add iommufd_hw_queue_depend/undepend() helpers iommufd/selftest: Add coverage for IOMMUFD_CMD_HW_QUEUE_ALLOC iommufd: Add mmap interface iommufd/selftest: Add coverage for the new mmap interface Documentation: userspace-api: iommufd: Update HW QUEUE iommu/arm-smmu-v3-iommufd: Add vsmmu_alloc impl op iommu/arm-smmu-v3-iommufd: Support implementation-defined hw_info iommu/tegra241-cmdqv: Use request_threaded_irq iommu/tegra241-cmdqv: Simplify deinit flow in tegra241_cmdqv_remove_vintf() iommu/tegra241-cmdqv: Do not statically map LVCMDQs iommu/tegra241-cmdqv: Add user-space use support iommu/tegra241-cmdqv: Add IOMMU_VEVENTQ_TYPE_TEGRA241_CMDQV support
drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h | 25 +- drivers/iommu/iommufd/io_pagetable.h | 8 + drivers/iommu/iommufd/iommufd_private.h | 28 +- drivers/iommu/iommufd/iommufd_test.h | 20 + include/linux/iommu.h | 43 +- include/linux/iommufd.h | 186 ++++++- include/uapi/linux/iommufd.h | 116 ++++- tools/testing/selftests/iommu/iommufd_utils.h | 52 +- .../arm/arm-smmu-v3/arm-smmu-v3-iommufd.c | 43 +- .../iommu/arm/arm-smmu-v3/tegra241-cmdqv.c | 490 +++++++++++++++++- drivers/iommu/iommufd/device.c | 117 +---- drivers/iommu/iommufd/driver.c | 94 ++++ drivers/iommu/iommufd/io_pagetable.c | 95 ++++ drivers/iommu/iommufd/main.c | 80 ++- drivers/iommu/iommufd/selftest.c | 133 ++++- drivers/iommu/iommufd/viommu.c | 121 ++++- tools/testing/selftests/iommu/iommufd.c | 97 +++- .../selftests/iommu/iommufd_fail_nth.c | 11 +- Documentation/userspace-api/iommufd.rst | 12 + 19 files changed, 1577 insertions(+), 194 deletions(-)
base-commit: 92a09c47464d040866cf2b4cd052bc60555185fb