# Re: \[PATCH\] Revert "powerpc/kernel/iommu: Align size for IOMMU\_PAGE\_SIZE() to save TCEs"

- From: Frederic Barrat \<hidden\>
- Date: 2021-05-27 06:10:45 
- List: linuxppc-dev
- Page: https://ratatoskr.run/linuxppc-dev/2021/05/9522899
- Thread: https://ratatoskr.run/linuxppc-dev/2021/05/9522894/t.md

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On 27/05/2021 04:13, Alexey Kardashevskiy wrote:
> On 27/05/2021 00:45, Frederic Barrat wrote:
>> This reverts commit 3c0468d4451eb6b4f6604370639f163f9637a479.
>>
>> That commit was breaking alignment guarantees for the DMA address when
>> allocating coherent mappings, as described in
>> Documentation/core-api/dma-api-howto.rst
>>
>> It was also noticed by Mellanox' driver:
>> [ 1515.763621] mlx5_core c002:01:00.0: mlx5_frag_buf_alloc_node:146:(pid 13402): unexpected map alignment: 0x0800000000c61000, page_shift=16
>> [ 1515.763635] mlx5_core c002:01:00.0: mlx5_cqwq_create:181:(pid
>> 13402): mlx5_frag_buf_alloc_node() failed, -12
>>
>> Signed-off-by: Frederic Barrat <redacted>
>
> Should it be
>
> Fixes: 3c0468d4451e ("powerpc/kernel/iommu: Align size for IOMMU_PAGE_SIZE() to save TCEs")
>
> ?


I had been wondering the same... I can see many revert commits with and without a "Fixes:" line. Since here the offending commit was merged in the latest merge window, I was thinking Fixes doesn't really bring anything, it will all stay internal to v5.13 development. I'd be happy to hear of the expected way of handling it. I'm guessing a big part of the answer is whether the tooling looking for a "Fixes" line is also looking for reverts.

  Fred



>
> Anyway,
>
> Reviewed-by: Alexey Kardashevskiy <redacted>

```