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From: Yihang Li <liyihang9@huawei.com>
To: Christoph Hellwig <hch@infradead.org>,
	John Garry <john.g.garry@oracle.com>
Cc: Damien Le Moal <dlemoal@kernel.org>, <yanaijie@huawei.com>,
	<jejb@linux.ibm.com>, <martin.petersen@oracle.com>,
	<chenxiang66@hisilicon.com>, <linux-scsi@vger.kernel.org>,
	<linux-kernel@vger.kernel.org>, <linuxarm@huawei.com>,
	<prime.zeng@huawei.com>, <yangxingui@huawei.com>,
	<liyihang9@huawei.com>
Subject: Re: [PATCH v2] scsi: libsas: Allocation SMP request is aligned to ARCH_DMA_MINALIGN
Date: Thu, 28 Mar 2024 14:59:40 +0800	[thread overview]
Message-ID: <75df3e2d-10c3-5370-3cd8-fe2fb0ff2acc@huawei.com> (raw)
In-Reply-To: <ZgUPpwhkE9bRwHec@infradead.org>



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

> 
> 
> .
> 

  reply	other threads:[~2024-03-28  6:59 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2024-03-26 12:43 Yihang Li
2024-03-26 13:14 ` Damien Le Moal
2024-03-26 13:32   ` John Garry
2024-03-26 13:40     ` Damien Le Moal
2024-03-28  6:35     ` Christoph Hellwig
2024-03-28  6:59       ` Yihang Li [this message]
2024-03-28  7:23         ` Damien Le Moal
2024-03-28  7:29           ` Christoph Hellwig
2024-03-28  7:36             ` Damien Le Moal
2024-03-28  7:45               ` Christoph Hellwig
2024-03-28  8:00                 ` Yihang Li

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