linux-kernel - Re: [PATCH v2] scsi: libsas: Allocation SMP request is aligned to ARCH_DMA

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Message-ID: <ba7d201b-3746-4ee1-9574-5782cccbc88e@kernel.org>
Date: Thu, 28 Mar 2024 16:36:12 +0900
From: Damien Le Moal <dlemoal@...nel.org>
To: Christoph Hellwig <hch@...radead.org>
Cc: Yihang Li <liyihang9@...wei.com>, John Garry <john.g.garry@...cle.com>,
 yanaijie@...wei.com, jejb@...ux.ibm.com, martin.petersen@...cle.com,
 chenxiang66@...ilicon.com, linux-scsi@...r.kernel.org,
 linux-kernel@...r.kernel.org, linuxarm@...wei.com, prime.zeng@...wei.com,
 yangxingui@...wei.com
Subject: Re: [PATCH v2] scsi: libsas: Allocation SMP request is aligned to
 ARCH_DMA_MINALIGN

On 3/28/24 16:29, Christoph Hellwig wrote:
> On Thu, Mar 28, 2024 at 04:23:22PM +0900, Damien Le Moal wrote:
>> But I thought that the original issue was that some arch have ARCH_DMA_MINALIGN
>> down to 8B but hisi driver needs at least 16 ?
>>
>> So in the end, you need something like:
>>
>> 	size = ALIGN(size, max(16, ARCH_DMA_MINALIGN));
>>
>> no ?
> 
> I don't think we ever have an 8 byte dma minalign.  With 8-byte
> aligned addresses dma_mapping_error could run into problems.

My bad: it is kmalloc() that can return something aligned to 8B...
So "size = ALIGN(size, ARCH_DMA_MINALIGN);" is the right thing to do.

-- 
Damien Le Moal
Western Digital Research