From: Mike Snitzer <snitzer@redhat.com>
Subject: Re: [PATCH v2 0/4] Introduce bulk mode for crypto engine framework
Date: Mon, 18 Apr 2016 09:36:12 -0400
Message-ID: <20160418133612.GA16853@redhat.com>
References: <cover.1458023695.git.baolin.wang@linaro.org>
 <20160415134849.GA32694@gondor.apana.org.au>
 <CAMz4ku+hXbgx1+YcdJWbCBW7KoeFisk5qcquAAg0fD5Qw5XDFQ@mail.gmail.com>
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Cc: Herbert Xu <herbert@gondor.apana.org.au>,
	David Miller <davem@davemloft.net>,
	Alasdair G Kergon <agk@redhat.com>,
	Jens Axboe <axboe@fb.com>, dm-devel@redhat.com,
	Andrew Morton <akpm@linux-foundation.org>,
	david.s.gordon@intel.com, Tom Lendacky <thomas.lendacky@amd.com>,
	Robert Jarzmik <robert.jarzmik@free.fr>,
	Masahiro Yamada <yamada.masahiro@socionext.com>,
	smueller@chronox.de, tadeusz.struk@intel.com,
	Masanari Iida <standby24x7@gmail.com>, shli@kernel.org,
	Mark Brown <broonie@kernel.org>,
	Linus Walleij <linus.walleij@linaro.org>,
	Arnd Bergmann <arnd@arndb.de>,
	LKML <linux-kernel@vger.kernel.org>,
	linux-crypto@vger.kernel.org, linux-raid@vger.kernel.org,
	Milan Broz <mbroz@redhat.com>
To: Baolin Wang <baolin.wang@linaro.org>
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On Mon, Apr 18 2016 at  1:31am -0400,
Baolin Wang <baolin.wang@linaro.org> wrote:

> Hi Herbert,
> 
> On 15 April 2016 at 21:48, Herbert Xu <herbert@gondor.apana.org.au> wrote:
> > On Tue, Mar 15, 2016 at 03:47:58PM +0800, Baolin Wang wrote:
> >> Now some cipher hardware engines prefer to handle bulk block by merging requests
> >> to increase the block size and thus increase the hardware engine processing speed.
> >>
> >> This patchset introduces request bulk mode to help the crypto hardware drivers
> >> improve in efficiency.
> >
> > Could you please explain why this merging can't be done in dm-crypt
> > instead?
> 
> We've tried to do this in dm-crypt, but it failed.
> The dm-crypt maintainer explained to me that I should optimize the
> driver, not add strange hw-dependent crypto modes to dm-crypt, this is
> not the first crypto accelerator that is just not suited for this kind
> of use.

As a DM mainatiner my only contribution to this line of discussion was
relative to your proposal to train the dm-crypt target (which is
bio-based) to also provide request-based support, see:
https://www.redhat.com/archives/dm-devel/2015-November/msg00112.html

But follow-up discussion occured, primarily with Milan Broz, which led
to this bulk mode support in the crypto layer.  Pretty strange Milan
wasn't cc'd on your patchset posting (I've now cc'd him).

Mike