Re: [PATCH v4 00/14] iommufd: Add vIOMMU infrastructure (Part-2: vDEVICE)

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On 22/10/24 11:20, Nicolin Chen wrote:
Following the previous vIOMMU series, this adds another vDEVICE structure,
representing the association from an iommufd_device to an iommufd_viommu.
This gives the whole architecture a new "v" layer:
   _______________________________________________________________________
  |                      iommufd (with vIOMMU/vDEVICE)                    |
  |                        _____________      _____________               |
  |                       |             |    |             |              |
  |      |----------------|    vIOMMU   |<---|   vDEVICE   |<------|      |
  |      |                |             |    |_____________|       |      |
  |      |     ______     |             |     _____________     ___|____  |
  |      |    |      |    |             |    |             |   |        | |
  |      |    | IOAS |<---|(HWPT_PAGING)|<---| HWPT_NESTED |<--| DEVICE | |
  |      |    |______|    |_____________|    |_____________|   |________| |
  |______|________|______________|__________________|_______________|_____|
         |        |              |                  |               |
   ______v_____   |        ______v_____       ______v_____       ___v__
  |   struct   |  |  PFN  |  (paging)  |     |  (nested)  |     |struct|
  |iommu_device|  |------>|iommu_domain|<----|iommu_domain|<----|device|
  |____________|   storage|____________|     |____________|     |______|

This vDEVICE object is used to collect and store all vIOMMU-related device
information/attributes in a VM. As an initial series for vDEVICE, add only
the virt_id to the vDEVICE, which is a vIOMMU specific device ID in a VM:
e.g. vSID of ARM SMMUv3, vDeviceID of AMD IOMMU, and vID of Intel VT-d to
a Context Table. This virt_id helps IOMMU drivers to link the vID to a pID
of the device against the physical IOMMU instance. This is essential for a
vIOMMU-based invalidation, where the request contains a device's vID for a
device cache flush, e.g. ATC invalidation.

Therefore, with this vDEVICE object, support a vIOMMU-based invalidation,
by reusing IOMMUFD_CMD_HWPT_INVALIDATE for a vIOMMU object to flush cache
with a given driver data.

As for the implementation of the series, add driver support in ARM SMMUv3
for a real world use case.

This series is on Github:
https://github.com/nicolinc/iommufd/commits/iommufd_viommu_p2-v4

For testing, try this "with-rmr" branch:
https://github.com/nicolinc/iommufd/commits/iommufd_viommu_p2-v4-with-rmr

Is there any real example of a .vdevice_alloc hook, besides the selftests? It is not in iommufd_viommu_p2-v4-with-rmr, hence the question. I am trying to sketch something with this new machinery and less guessing would be nice. Thanks,


Paring QEMU branch for testing:
https://github.com/nicolinc/qemu/commits/wip/for_iommufd_viommu_p2-v4

Changelog
v4
  * Added missing brackets in switch-case
  * Fixed the unreleased idev refcount issue
  * Reworked the iommufd_vdevice_alloc allocator
  * Dropped support for IOMMU_VIOMMU_TYPE_DEFAULT
  * Added missing TEST_LENGTH and fail_nth coverages
  * Added a verification to the driver-allocated vDEVICE object
  * Added an iommufd_vdevice_abort for a missing mutex protection
  * Added a u64 structure arm_vsmmu_invalidation_cmd for user command
    conversion
v3
  https://lore.kernel.org/all/cover.1728491532.git.nicolinc@xxxxxxxxxx/
  * Added Jason's Reviewed-by
  * Split this invalidation part out of the part-1 series
  * Repurposed VDEV_ID ioctl to a wider vDEVICE structure and ioctl
  * Reduced viommu_api functions by allowing drivers to access viommu
    and vdevice structure directly
  * Dropped vdevs_rwsem by using xa_lock instead
  * Dropped arm_smmu_cache_invalidate_user
v2
  https://lore.kernel.org/all/cover.1724776335.git.nicolinc@xxxxxxxxxx/
  * Limited vdev_id to one per idev
  * Added a rw_sem to protect the vdev_id list
  * Reworked driver-level APIs with proper lockings
  * Added a new viommu_api file for IOMMUFD_DRIVER config
  * Dropped useless iommu_dev point from the viommu structure
  * Added missing index numnbers to new types in the uAPI header
  * Dropped IOMMU_VIOMMU_INVALIDATE uAPI; Instead, reuse the HWPT one
  * Reworked mock_viommu_cache_invalidate() using the new iommu helper
  * Reordered details of set/unset_vdev_id handlers for proper lockings
v1
  https://lore.kernel.org/all/cover.1723061377.git.nicolinc@xxxxxxxxxx/

Thanks!
Nicolin

Jason Gunthorpe (2):
   iommu: Add iommu_copy_struct_from_full_user_array helper
   iommu/arm-smmu-v3: Allow ATS for IOMMU_DOMAIN_NESTED

Nicolin Chen (12):
   iommufd/viommu: Introduce IOMMUFD_OBJ_VDEVICE and its related struct
   iommufd/viommu: Add IOMMU_VDEVICE_ALLOC ioctl
   iommufd/selftest: Add IOMMU_VDEVICE_ALLOC test coverage
   iommu/viommu: Add cache_invalidate to iommufd_viommu_ops
   iommufd/hw_pagetable: Enforce cache invalidation op on vIOMMU-based
     hwpt_nested
   iommufd: Allow hwpt_id to carry viommu_id for IOMMU_HWPT_INVALIDATE
   iommufd/viommu: Add vdev_to_dev helper
   iommufd/selftest: Add mock_viommu_cache_invalidate
   iommufd/selftest: Add IOMMU_TEST_OP_DEV_CHECK_CACHE test command
   iommufd/selftest: Add vIOMMU coverage for IOMMU_HWPT_INVALIDATE ioctl
   Documentation: userspace-api: iommufd: Update vDEVICE
   iommu/arm-smmu-v3: Add arm_vsmmu_cache_invalidate

  drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h   |   9 +-
  drivers/iommu/iommufd/iommufd_private.h       |  12 ++
  drivers/iommu/iommufd/iommufd_test.h          |  30 +++
  include/linux/iommu.h                         |  49 ++++-
  include/linux/iommufd.h                       |  50 +++++
  include/uapi/linux/iommufd.h                  |  61 +++++-
  tools/testing/selftests/iommu/iommufd_utils.h |  83 +++++++
  .../arm/arm-smmu-v3/arm-smmu-v3-iommufd.c     | 162 +++++++++++++-
  drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c   |  32 ++-
  drivers/iommu/iommufd/device.c                |  11 +
  drivers/iommu/iommufd/driver.c                |   7 +
  drivers/iommu/iommufd/hw_pagetable.c          |  36 +++-
  drivers/iommu/iommufd/main.c                  |   7 +
  drivers/iommu/iommufd/selftest.c              | 115 +++++++++-
  drivers/iommu/iommufd/viommu.c                | 108 ++++++++++
  tools/testing/selftests/iommu/iommufd.c       | 204 +++++++++++++++++-
  .../selftests/iommu/iommufd_fail_nth.c        |   4 +
  Documentation/userspace-api/iommufd.rst       |  41 +++-
  18 files changed, 983 insertions(+), 38 deletions(-)


--
Alexey





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