[PATCH v10 0/7] Linux RISC-V IOMMU Support

[Tomasz Jeznach]

This patch series introduces support for RISC-V IOMMU architected
hardware into the Linux kernel.

The RISC-V IOMMU specification, which this series is based on, is
ratified and available at GitHub/riscv-non-isa [1].

At a high level, the RISC-V IOMMU specification defines:

1) Data structures:
  - Device-context: Associates devices with address spaces and holds
    per-device parameters for address translations.
  - Process-contexts: Associates different virtual address spaces based
    on device-provided process identification numbers.
  - MSI page table configuration used to direct an MSI to a guest
    interrupt file in an IMSIC.
2) In-memory queue interface:
  - Command-queue for issuing commands to the IOMMU.
  - Fault/event queue for reporting faults and events.
  - Page-request queue for reporting "Page Request" messages received
    from PCIe devices.
  - Message-signaled and wire-signaled interrupt mechanisms.
3) Memory-mapped programming interface:
  - Mandatory and optional register layout and description.
  - Software guidelines for device initialization and capabilities discovery.


This series introduces RISC-V IOMMU hardware initialization and complete
single-stage translation with paging domain support.

The patches are organized as follows:

Patch 1: Introduces minimal required device tree bindings for the driver.
Patch 2: Defines RISC-V IOMMU data structures, hardware programming interface
         registers layout, and minimal initialization code for enabling global
         pass-through for all connected masters.
Patch 3: Implements the device driver for PCIe implementation of RISC-V IOMMU
         architected hardware.
Patch 4: Introduces IOMMU interfaces to the kernel subsystem.
Patch 5: Implements device directory management with discovery sequences for
         I/O mapped or in-memory device directory table location, hardware
         capabilities discovery, and device to domain attach implementation.
Patch 6: Implements command and fault queue, and introduces directory cache
         invalidation sequences.
Patch 7: Implements paging domain, using highest page-table mode advertised
         by the hardware. This series enables only 4K mappings; complete support
         for large page mappings will be introduced in follow-up patch series.

Follow-up patch series providing MSI interrupt remapping, complete ATS/PRI/SVA
and VFIO/IOMMUFD support are available at the GitHub [2], and has been tested
with published QEMU RISC-V IOMMU device model [3].

Changes from v9:
- rebase on v6.12-rc3
- #6 Memory ordering fix and updated commentary, based on Will’s suggestions.
- #7 Remove riscv_iommu_device_domain_type() and use head-less kfree_rcu in
     riscv_iommu_release_device(), based on Jason's suggestions.

Best regards,
 Tomasz Jeznach

[1] link: https://github.com/riscv-non-isa/riscv-iommu
[2] link: https://github.com/tjeznach/linux/riscv_iommu.next
[3] link: https://lore.kernel.org/qemu-devel/20241004155721.2154626-1-dbarboza@ventanamicro.com/
v9 link:  https://lore.kernel.org/linux-iommu/cover.1728579958.git.tjeznach@rivosinc.com/
v8 link:  https://lore.kernel.org/linux-iommu/cover.1718388908.git.tjeznach@rivosinc.com/
v7 link:  https://lore.kernel.org/linux-iommu/cover.1717612298.git.tjeznach@rivosinc.com/
v6 link:  https://lore.kernel.org/linux-iommu/cover.1716578450.git.tjeznach@rivosinc.com/
v5 link:  https://lore.kernel.org/linux-iommu/cover.1715708679.git.tjeznach@rivosinc.com/
v4 link:  https://lore.kernel.org/linux-iommu/cover.1714752293.git.tjeznach@rivosinc.com/
v3 link:  https://lore.kernel.org/linux-iommu/cover.1714494653.git.tjeznach@rivosinc.com/
v2 link:  https://lore.kernel.org/linux-iommu/cover.1713456597.git.tjeznach@rivosinc.com/
v1 link:  https://lore.kernel.org/linux-iommu/cover.1689792825.git.tjeznach@rivosinc.com/

Tomasz Jeznach (7):
  dt-bindings: iommu: riscv: Add bindings for RISC-V IOMMU
  iommu/riscv: Add RISC-V IOMMU platform device driver
  iommu/riscv: Add RISC-V IOMMU PCIe device driver
  iommu/riscv: Enable IOMMU registration and device probe.
  iommu/riscv: Device directory management.
  iommu/riscv: Command and fault queue support
  iommu/riscv: Paging domain support

 .../bindings/iommu/riscv,iommu.yaml           |  147 ++
 MAINTAINERS                                   |    9 +
 drivers/iommu/Kconfig                         |    1 +
 drivers/iommu/Makefile                        |    2 +-
 drivers/iommu/riscv/Kconfig                   |   20 +
 drivers/iommu/riscv/Makefile                  |    3 +
 drivers/iommu/riscv/iommu-bits.h              |  784 ++++++++
 drivers/iommu/riscv/iommu-pci.c               |  120 ++
 drivers/iommu/riscv/iommu-platform.c          |   92 +
 drivers/iommu/riscv/iommu.c                   | 1661 +++++++++++++++++
 drivers/iommu/riscv/iommu.h                   |   88 +
 11 files changed, 2926 insertions(+), 1 deletion(-)
 create mode 100644 Documentation/devicetree/bindings/iommu/riscv,iommu.yaml
 create mode 100644 drivers/iommu/riscv/Kconfig
 create mode 100644 drivers/iommu/riscv/Makefile
 create mode 100644 drivers/iommu/riscv/iommu-bits.h
 create mode 100644 drivers/iommu/riscv/iommu-pci.c
 create mode 100644 drivers/iommu/riscv/iommu-platform.c
 create mode 100644 drivers/iommu/riscv/iommu.c
 create mode 100644 drivers/iommu/riscv/iommu.h


base-commit: 8e929cb546ee42c9a61d24fae60605e9e3192354
-- 
2.34.1