linux-kernel - Re: [PATCH] iommu/dma: Zero pages manually in a length of scatterlist

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Message-ID: <20181105145847.GA31337@infradead.org>
Date:   Mon, 5 Nov 2018 06:58:47 -0800
From:   Christoph Hellwig <hch@...radead.org>
To:     Nicolin Chen <nicoleotsuka@...il.com>
Cc:     Robin Murphy <robin.murphy@....com>, joro@...tes.org,
        iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] iommu/dma: Zero pages manually in a length of scatterlist

On Fri, Nov 02, 2018 at 04:36:13PM -0700, Nicolin Chen wrote:
> > What if the pages came from highmem? I know that doesn't happen on arm64
> > today, but the point of this code *is* to be generic, and other users will
> > arrive eventually.
> 
> Hmm, so it probably should use sg_miter_start/stop() too? Looking
> at the flush routine doing in PAGE_SIZE for each iteration, would
> be possible to map and memset contiguous pages together? Actually
> the flush routine might be also optimized if we can map contiguous
> pages.

FYI, I have patches I plan to submit soon that gets rid of the
struct scatterlist use in this code to simplify it:

http://git.infradead.org/users/hch/misc.git/commitdiff/84e837fc3248b513f73adde49e04e7c58f605113