Re: [PATCH v3 0/4] Introduce vfio_dma_mapping_perf_test

[David Matlack <dmatlack@google.com>]

On 2026-09-10 03:33 PM, Aaron Lewis wrote:
> Add a new VFIO selftest, vfio_dma_mapping_perf_test, to provide a
> configurable tool for measuring DMA mapping and unmapping latencies.
> 
> This selftest introduces command-line parameters to provide a convenient
> way to tune the test for specific situations. For example, it can be used
> to observe the lengthy unmap times of the Type 1 IOMMU on large memory
> regions, or to compare DMA mapping performance between the Type 1 IOMMU
> and IOMMUFD. These scenarios can now be easily configured and run via the
> command line.
> 
> Changes in v3:
>  - Replaced raw printf() calls with ksft_print_msg()
>  - Updated the TIME macro to preserve errno
>  - Added 'fd' and 'fd_offset' to struct dma_region
>  - Simplified teardown_memfd() by removing redundant error checks
>  - Replaced the command-line argument passthrough (-a "...") approach with
>    first-class support in kselftest_harness.h

This looks a lot better, thanks for making the change!

>  - Added collision validation in optstring_append_custom() to prevent custom
>    options from overlapping with built-in harness options.
>  - Switched test_enabled() to match exact option characters rather than
>    tolower(opt), ensuring custom options that differ only by case (such as
>    'R') do not mistakenly match built-in single-case options like '-r'.
> 
> Aaron Lewis (4):
>   vfio: selftests: Assert the region was unmapped in iommu_unmap()
>   vfio: selftests: Introduce vfio_dma_mapping_perf_test
>   vfio: selftests: Add memfd test to vfio_dma_mapping_perf_test
>   vfio: selftests: Allow a size for vfio_dma_mapping_perf_test
> 
>  tools/testing/selftests/kselftest_harness.h   |  86 +++++-
>  tools/testing/selftests/vfio/Makefile         |   1 +
>  .../selftests/vfio/lib/include/libvfio.h      |  31 +++
>  .../vfio/lib/include/libvfio/iommu.h          |  14 +-
>  tools/testing/selftests/vfio/lib/iommu.c      |  24 ++
>  .../vfio/vfio_dma_mapping_perf_test.c         | 263 ++++++++++++++++++
>  .../selftests/vfio/vfio_dma_mapping_test.c    |  11 +-
>  7 files changed, 406 insertions(+), 24 deletions(-)
>  create mode 100644 tools/testing/selftests/vfio/vfio_dma_mapping_perf_test.c
> 
> -- 
> 2.55.0.1003.g10538fe699-goog
>