Re: [RFC PATCH 0/6] selftests/vfio: Add sPAPR TCE v2 coverage

[Harsh Prateek Bora <harshpb@linux.ibm.com>]

+ linuxppc-dev

On 03/07/26 8:58 am, Narayana Murty N wrote:
> This RFC adds PowerPC sPAPR TCE v2 support to VFIO selftests.
> 
> The series adds a selftest IOMMU mode for the legacy VFIO container
> backend, adds helpers for default and dynamic DMA windows, and exercises
> the sPAPR DDW path through the DMA mapping tests.
> 
> sPAPR TCE v2 remains a legacy VFIO container backend. This series does
> not add iommufd or VFIO cdev support for sPAPR.
> 
> The main points are
> 1. add VFIO_SELFTESTS_IOMMU_MODE for selecting a backend
> 2. add vfio_spapr_tce_v2_iommu as the PowerPC VFIO backend
> 3. preserve the platform default DMA window
> 4. create and tear down only selftest-created DDWs
> 5. prepare the DMA window before IOVA allocation
> 6. exercise DDW creation for hugepage DMA mappings
> 7. accept sPAPR-specific errno for invalid DMA ranges
> 
> Example:
> 
> VFIO_SELFTESTS_IOMMU_MODE=vfio_spapr_tce_v2_iommu
> ./vfio_dma_mapping_test <BDF>
> 
> Observed coverage includes anonymous mappings through the default window
> and 2MB hugetlb mappings through a DDW. 1GB hugetlb mappings may skip when
> the platform rejects the requested DDW characteristics.
> 
> Feedback is requested from the VFIO and PowerPC communities on:
> 1. whether the sPAPR TCE v2 helpers should remain in the common VFIO
> selftest library or move into a sPAPR-specific test helper?
> 2. whether DDW setup through hugepage mappings is the right initial
> coverage?
> 3. whether the sPAPR-specific overflow errno expectation should be
> accepted, skipped, or hidden behind a backend helper?
> 4. whether PowerPC should generate only the sPAPR TCE v2 fixture variants,
> or keep the generic IOMMU-mode matrix and skip unsupported modes.
> 
> TODO: vfio_spapr_tce_v1_iommu yet to be covered.
> 
> Narayana Murty N (6):
>    selftests/vfio: allow selecting IOMMU backend from environment
>    selftests/vfio: add sPAPR TCE v2 IOMMU mode
>    selftests/vfio: add sPAPR TCE v2 DMA window helpers
>    selftests/vfio: Exercise sPAPR DDW path for hugepage DMA mappings
>    selftests/vfio: Accept sPAPR errno for DMA range overflow
>    selftests/vfio: Enable VFIO selftests on ppc64 and ppc64le
> 
>   .../selftests/vfio/lib/include/libvfio.h      |   9 +
>   .../vfio/lib/include/libvfio/iommu.h          |  26 ++
>   tools/testing/selftests/vfio/lib/iommu.c      | 280 +++++++++++++++++-
>   tools/testing/selftests/vfio/lib/libvfio.c    |  37 +++
>   .../selftests/vfio/vfio_dma_mapping_test.c    |  30 ++
>   .../selftests/vfio/vfio_pci_device_test.c     |   4 +-
>   tools/testing/selftests/vfio/Makefile         |   2 +-
>   7 files changed, 382 insertions(+), 6 deletions(-)
>