Re: [PATCH] Revert "powerpc/kernel/iommu: Align size for IOMMU_PAGE_SIZE() to save TCEs"

[Frederic Barrat <fbarrat@linux.ibm.com>]

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 <fbarrat@linux.ibm.com>
> 
> 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 <aik@ozlabs.ru>