linux-kernel - Re: Is it needed to zero out the dma buffer for DMA_ATTR_NO_KERNEL

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Message-ID: <bee6cbc9-f637-9217-5f1b-086d93295f70@samsung.com>
Date:   Fri, 4 Sep 2020 11:10:46 +0200
From:   Marek Szyprowski <m.szyprowski@...sung.com>
To:     Hillf Danton <hdanton@...a.com>, Christoph Hellwig <hch@....de>
Cc:     Kees Cook <keescook@...omium.org>, linux-nvme@...ts.infradead.org,
        linux-kernel@...r.kernel.org,
        James Bottomley <James.Bottomley@...senPartnership.com>,
        Matthew Wilcox <willy@...radead.org>
Subject: Re: Is it needed to zero out the dma buffer for
 DMA_ATTR_NO_KERNEL_MAPPING

Hi

On 04.09.2020 04:28, Hillf Danton wrote:
> Currently the DMA_ATTR_NO_KERNEL_MAPPING buffer allocated is not
> cleared while dma core always zero it out for coherent allocations.
>
> Is it making sense to do memset for the attr?

If it is not cleared then this is a bug. Please propose a patch fixing 
this issue.

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