Re: [PATCH] mm/slab: align kmalloc to cacheline when DMA API debugging is active

[Marek Szyprowski]

On 27.03.2026 15:37, Mikhail Gavrilov wrote:
> On Fri, Mar 27, 2026 at 7:30 PM Vlastimil Babka (SUSE)
> <vbabka@xxxxxxxxxx> wrote:
>> So what about Harry's proposal [1]? Mikhail seems to be on board? [2]
>>
>> It seems it would achieve the goal that enabling DMA_API_DEBUG doesn't
>> change the kernel behavior? But I don't know this area too well so
>> maybe there's a catch.
>>
>> [1] https://lore.kernel.org/all/acYlxRBhSMcwBnja@hyeyoo/
>> [2] https://lore.kernel.org/all/CABXGCsO_C8%2B%2B4%2BoPfZ%2BbQyrBnEGy5JFpXHkGNpfy%2B8%3D5BvVNfg@xxxxxxxxxxxxxx/
> Hi Vlastimil,
>
> Yes, I've already sent v2 based on Harry's suggestion:
> https://lore.kernel.org/all/20260327124156.24820-1-mikhail.v.gavrilov@xxxxxxxxx/
>
> It adds a dma_get_cache_alignment() >= L1_CACHE_BYTES check in
> add_dma_entry() instead of changing ARCH_KMALLOC_MINALIGN, so
> enabling DMA_API_DEBUG no longer affects allocator behavior.

This looks like a good fix, but let me think a bit more about all 
possible cases.

Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland