Messages in this thread | | | From | John Garry <> | Subject | [PATCH 0/4] DMA mapping changes for SCSI core | Date | Fri, 20 May 2022 16:23:19 +0800 |
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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]. An alternative to adding the new API would be to add a "hard_limit" arg to dma_max_mapping_size(). This would mean fixing up all current users, but it would be good to do that anyway as not all users require a hard limit.
The SCSI core coded 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.
[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/
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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