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From: Christoph Hellwig <hch@infradead.org>
To: Robin Murphy <robin.murphy@arm.com>
Cc: Christoph Hellwig <hch@infradead.org>,
	Nicolin Chen <nicoleotsuka@gmail.com>,
	joro@8bytes.org, iommu@lists.linux-foundation.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH] iommu/dma: Zero pages manually in a length of scatterlist
Date: Thu, 8 Nov 2018 23:45:10 -0800	[thread overview]
Message-ID: <20181109074510.GA27623@infradead.org> (raw)
In-Reply-To: <afdc0e33-db18-6ad9-61cd-919fe3df1b4e@arm.com>

On Tue, Nov 06, 2018 at 02:39:26PM +0000, Robin Murphy wrote:
> ...and I have some significant objections to that simplification which I
> plan to respond with ;)
> 
> (namely that it defaults the whole higher-order page allocation business
> which will have varying degrees of performance impact on certain cases)

Well, please place your objection there.  The behavior does match what
every other iommu-based dma ops implementation ouside of arm/arm64 does,
so there is some precedent for it to say the least.  But if the only
current users objects I'll surely find a way to accomodate it, but a
good rationale including numbers would be useful to document it.

  reply	other threads:[~2018-11-09  7:45 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-11-01 21:35 [PATCH] iommu/dma: Zero pages manually in a length of scatterlist Nicolin Chen
2018-11-02 16:54 ` Robin Murphy
2018-11-02 23:36   ` Nicolin Chen
2018-11-05 14:58     ` Christoph Hellwig
2018-11-06 14:39       ` Robin Murphy
2018-11-09  7:45         ` Christoph Hellwig [this message]
2018-11-06 18:27     ` Robin Murphy
2018-11-07  0:11       ` Nicolin Chen
2018-11-04 15:50 ` Christoph Hellwig
2018-11-06 23:46   ` Nicolin Chen

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