On 30/06/2022 13:08, John Garry wrote:

Hi Christoph,

Can you please consider picking up this series? A few things to note beforehand:

- I changed to only apply the mapping limit to SAS hosts in this version. I would need a fresh ack from Martin for those SCSI parts, but wanted to make sure you were ok with it. - Damien had some doubt on updating the shost max_sectors as opposed to the per-request queue default, but I think he's ok with it - see patch 4/5


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

The SCSI SAS transport code is modified only to use this limit. For now I
did not want to touch other hosts as I have a concern that this change
could cause a performance regression.

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


Changes since v4:
- tweak libata and other patch titles
- Add Robin's tag (thanks!)
- Clarify description of new DMA mapping API

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