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[v1,00/16] iommufd: Add vIOMMU infrastructure (Part-4 vCMDQ)

Message ID cover.1744353300.git.nicolinc@nvidia.com
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Series iommufd: Add vIOMMU infrastructure (Part-4 vCMDQ) | expand

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Nicolin Chen April 11, 2025, 6:37 a.m. UTC 
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 is on Github:
https://github.com/nicolinc/iommufd/commits/iommufd_vcmdq-v1

Paring QEMU branch for testing:
https://github.com/nicolinc/qemu/commits/wip/for_iommufd_vcmdq-v1

Thanks
Nicolin

Nicolin Chen (16):
  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/viommu: Add driver-allocated vDEVICE support
  iommufd/viommu: Introduce IOMMUFD_OBJ_VCMDQ and its related struct
  iommufd/viommmu: Add IOMMUFD_CMD_VCMDQ_ALLOC ioctl
  iommufd: Add mmap interface
  iommufd/selftest: Add coverage for the new mmap interface
  Documentation: userspace-api: iommufd: Update vCMDQ
  iommu/tegra241-cmdqv: Use request_threaded_irq
  iommu/arm-smmu-v3: Add vsmmu_alloc impl op
  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   |  24 +-
 drivers/iommu/iommufd/iommufd_private.h       |  20 +-
 drivers/iommu/iommufd/iommufd_test.h          |  17 +
 include/linux/iommu.h                         |  43 ++-
 include/linux/iommufd.h                       |  93 +++++
 include/uapi/linux/iommufd.h                  |  87 +++++
 tools/testing/selftests/iommu/iommufd_utils.h |  21 +-
 .../arm/arm-smmu-v3/arm-smmu-v3-iommufd.c     |  26 +-
 .../iommu/arm/arm-smmu-v3/tegra241-cmdqv.c    | 349 +++++++++++++++++-
 drivers/iommu/iommufd/driver.c                |  54 +++
 drivers/iommu/iommufd/main.c                  |  54 ++-
 drivers/iommu/iommufd/selftest.c              |  58 ++-
 drivers/iommu/iommufd/viommu.c                |  78 +++-
 tools/testing/selftests/iommu/iommufd.c       |  34 +-
 .../selftests/iommu/iommufd_fail_nth.c        |   5 +-
 Documentation/userspace-api/iommufd.rst       |  11 +
 16 files changed, 912 insertions(+), 62 deletions(-)

Comments

ALOK TIWARI April 11, 2025, 12:35 p.m. UTC | #1 
On 11-04-2025 12:07, Nicolin Chen wrote:
> + * iommu_copy_struct_to_user - Report iommu driver specific user space data
> + * @user_data: Pointer to a struct iommu_user_data for user space data location
> + * @ksrc: Pointer to an iommu driver specific user data that is defined in
> + *        include/uapi/linux/iommufd.h
> + * @data_type: The data type of the @ksrc. Must match with @user_data->type
> + * @min_last: The last memember of the data structure @ksrc points in the

old typo  memember -> member

> + *            initial version.
> + * Return 0 for success, otherwise -error.


Thanks,
Alok
Nicolin Chen April 14, 2025, 6:03 p.m. UTC | #2 
On Fri, Apr 11, 2025 at 06:05:30PM +0530, ALOK TIWARI wrote:
> On 11-04-2025 12:07, Nicolin Chen wrote:
> > + * iommu_copy_struct_to_user - Report iommu driver specific user space data
> > + * @user_data: Pointer to a struct iommu_user_data for user space data location
> > + * @ksrc: Pointer to an iommu driver specific user data that is defined in
> > + *        include/uapi/linux/iommufd.h
> > + * @data_type: The data type of the @ksrc. Must match with @user_data->type
> > + * @min_last: The last memember of the data structure @ksrc points in the
> 
> old typo  memember -> member

Fixed for this one.

And yea, we need a patch fixing iommu_copy_struct_from_user() too.

Thanks
Nicolin