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    Subject[PATCH v3 0/4] DMA mapping changes for SCSI core
    Date
    As reported in [0], DMA mappings whose size exceeds the IOMMU IOVA caching
    limit may see a big performance hit.

    This series introduces a new DMA mapping API, dma_opt_mapping_size(), so
    that drivers may know this limit when performance is a factor in the
    mapping.

    Robin didn't like using dma_max_mapping_size() for this [1].

    The SCSI core code is modified to use this limit.

    I also added a patch for libata-scsi as it does not currently honour the
    shost max_sectors limit.

    Note: Christoph has previously kindly offered to take this series via the
    dma-mapping tree, so I think that we just need an ack from the
    IOMMU guys now.

    [0] https://lore.kernel.org/linux-iommu/20210129092120.1482-1-thunder.leizhen@huawei.com/
    [1] https://lore.kernel.org/linux-iommu/f5b78c9c-312e-70ab-ecbb-f14623a4b6e3@arm.com/

    Changes since v2:
    - Rebase on v5.19-rc1
    - Add Damien's tag to 2/4 (thanks)

    Changes since v1:
    - Relocate scsi_add_host_with_dma() dma_dev check (Reported by Dan)
    - Add tags from Damien and Martin (thanks)
    - note: I only added Martin's tag to the SCSI patch

    John Garry (4):
    dma-mapping: Add dma_opt_mapping_size()
    dma-iommu: Add iommu_dma_opt_mapping_size()
    scsi: core: Cap shost max_sectors according to DMA optimum mapping
    limits
    libata-scsi: Cap ata_device->max_sectors according to
    shost->max_sectors

    Documentation/core-api/dma-api.rst | 9 +++++++++
    drivers/ata/libata-scsi.c | 1 +
    drivers/iommu/dma-iommu.c | 6 ++++++
    drivers/iommu/iova.c | 5 +++++
    drivers/scsi/hosts.c | 5 +++++
    drivers/scsi/scsi_lib.c | 4 ----
    include/linux/dma-map-ops.h | 1 +
    include/linux/dma-mapping.h | 5 +++++
    include/linux/iova.h | 2 ++
    kernel/dma/mapping.c | 12 ++++++++++++
    10 files changed, 46 insertions(+), 4 deletions(-)

    --
    2.26.2

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