linux-kernel - Re: [PATCH v5 4/4] crypto: Add Allwinner Security System crypto accelerator

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Date:	Sun, 16 Nov 2014 18:13:14 +0100
From:	Maxime Ripard <maxime.ripard@...e-electrons.com>
To:	Herbert Xu <herbert@...dor.apana.org.au>
Cc:	Corentin LABBE <clabbe.montjoie@...il.com>, robh+dt@...nel.org,
	pawel.moll@....com, mark.rutland@....com,
	ijc+devicetree@...lion.org.uk, galak@...eaurora.org,
	linux@....linux.org.uk, davem@...emloft.net,
	grant.likely@...aro.org, akpm@...ux-foundation.org,
	gregkh@...uxfoundation.org, joe@...ches.com,
	mchehab@....samsung.com, crope@....fi, devicetree@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	linux-crypto@...r.kernel.org, linux-sunxi@...glegroups.com
Subject: Re: [PATCH v5 4/4] crypto: Add Allwinner Security System crypto
 accelerator

On Thu, Nov 06, 2014 at 10:32:18PM +0800, Herbert Xu wrote:
> On Thu, Nov 06, 2014 at 03:26:33PM +0100, Maxime Ripard wrote:
> > 
> > But you still haven't explain why the driver, while it doesn't handle
> > the user space buffer at any time, should be worried that the data the
> > framework has given him are actually mapped.
> 
> Encryption is used by IPsec and SKBs can be allocated in highmem.
> algif also exposes all ciphers to user-space memory which can also
> be in highmem.

Ok. We keep going in circles here.

I know that algif handles userspace memory that can be in
highmem. What I don't get, is that just like a *driver* doesn't have
to call copy_from_user, why would it need to call kmap...

That's something that should be in the framework itself, not the
driver. And the argument that most drivers use DMA seems like a broken
assumption.

But hey, you're the one that will maintain this mess, so I guess you
have the final word.

Maxime

-- 
Maxime Ripard, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com

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