Message-ID: <cover.1745646960.git.nicolinc@nvidia.com>
Date: Fri, 25 Apr 2025 22:57:55 -0700
From: Nicolin Chen <nicolinc@...dia.com>
To: <jgg@...dia.com>, <kevin.tian@...el.com>, <corbet@....net>,
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Subject: [PATCH v2 00/22] iommufd: Add vIOMMU infrastructure (Part-4 vCMDQ)

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.

A vCMDQ introduced by this series as a part of the vIOMMU infrastructure
represents a HW supported queue/buffer for VM to use exclusively, e.g.
  - NVIDIA's virtual command queue
  - AMD vIOMMU's command buffer
either of which is an IOMMU HW feature to directly load and execute cache
invalidation commands issued by a guest kernel, to shoot down TLB entries
that HW cached for guest-owned stage-1 page table entries. This is a big
improvement since there is no VM Exit during an invalidation, compared to
the traditional invalidation pathway by trapping a guest-own invalidation
queue and forwarding those commands/requests to the host kernel that will
eventually fill a HW-owned queue to execute those commands.

Thus, a vCMDQ object, as an initial use case, is all about a guest-owned
HW command queue that VMM can allocate/configure depending on the request
from a guest kernel. Introduce a new IOMMUFD_OBJ_VCMDQ and its allocator
IOMMUFD_CMD_VCMDQ_ALLOC allowing VMM to forward the IOMMU-specific queue
info, such as queue base address, size, and etc.

Meanwhile, a guest-owned command queue needs the kernel (a command queue
driver) to control the queue by reading/writing its consumer and producer
indexes, which means the command queue HW allows the guest kernel to get
a direct R/W access to those registers. Introduce an mmap infrastructure
to the iommufd core so as to support pass through a piece of MMIO region
from the host physical address space to the guest physical address space.
The VMA info (vm_pgoff/size) used by an mmap must be pre-allocated during
the IOMMUFD_CMD_VCMDQ_ALLOC and given those info to the user space as an
output driver-data by the IOMMUFD_CMD_VCMDQ_ALLOC. So, this requires a
driver-specific user data support by a vIOMMU object.

As a real-world use case, this series implements a vCMDQ support to the
tegra241-cmdqv driver for the vCMDQ on NVIDIA Grace CPU. In another word,
this 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.

This is on Github:
https://github.com/nicolinc/iommufd/commits/iommufd_vcmdq-v2

Paring QEMU branch for testing:
https://github.com/nicolinc/qemu/commits/wip/for_iommufd_vcmdq-v2

Changelog
v2
 * 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 (22):
  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: 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_VCMDQ and its related struct
  iommufd/viommmu: Add IOMMUFD_CMD_VCMDQ_ALLOC ioctl
  iommufd: Add for-driver helpers iommufd_vcmdq_depend/undepend()
  iommufd/selftest: Add coverage for IOMMUFD_CMD_VCMDQ_ALLOC
  iommufd: Add mmap interface
  iommufd/selftest: Add coverage for the new mmap interface
  Documentation: userspace-api: iommufd: Update vCMDQ
  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       |  25 +-
 drivers/iommu/iommufd/iommufd_test.h          |  20 +
 include/linux/iommu.h                         |  43 +-
 include/linux/iommufd.h                       | 146 ++++++
 include/uapi/linux/iommufd.h                  | 113 ++++-
 tools/testing/selftests/iommu/iommufd_utils.h |  51 +-
 .../arm/arm-smmu-v3/arm-smmu-v3-iommufd.c     |  42 +-
 .../iommu/arm/arm-smmu-v3/tegra241-cmdqv.c    | 451 +++++++++++++++++-
 drivers/iommu/iommufd/device.c                | 117 +----
 drivers/iommu/iommufd/driver.c                |  81 ++++
 drivers/iommu/iommufd/io_pagetable.c          |  95 ++++
 drivers/iommu/iommufd/main.c                  |  58 ++-
 drivers/iommu/iommufd/selftest.c              | 123 ++++-
 drivers/iommu/iommufd/viommu.c                | 111 ++++-
 tools/testing/selftests/iommu/iommufd.c       |  93 +++-
 .../selftests/iommu/iommufd_fail_nth.c        |  11 +-
 Documentation/userspace-api/iommufd.rst       |  14 +
 19 files changed, 1436 insertions(+), 191 deletions(-)

-- 
2.43.0

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