Re: [PATCH v2] scsi: libsas: Allocation SMP request is aligned to ARCH_DMA_MINALIGN

[Yihang Li]

On 2024/3/28 14:35, Christoph Hellwig wrote:
> On Tue, Mar 26, 2024 at 01:32:09PM +0000, John Garry wrote:
>>>> +	u8 *p;
>>>> +
>>>> +	size = ALIGN(size, ARCH_DMA_MINALIGN);
>>
>>
>> If this is a hisi_sas requirement, then why use ARCH_DMA_MINALIGN and not
>> 16B as minimum alignment?
>>
>> Or are we really talking about an arch requirement?
> 
> One thing is that we should never allocate unaligned memory for
> anything DMA mapped, or data will be corrupted by non-coherent DMA.
> So ARCH_DMA_MINALIGN needs to be here.  If specific hardware has
> further requirements we'll need to communicated it through a field
> or op vector.

Got it. Looks like it's still going to be aligned to ARCH_DMA_MINALIGN.

Thanks,
Yihang

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