linux-kernel - Re: [PATCH v2 0/4] Introduce bulk mode for crypto engine framework

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Date:	Mon, 18 Apr 2016 16:14:48 +0800
From:	Baolin Wang <baolin.wang@...aro.org>
To:	Herbert Xu <herbert@...dor.apana.org.au>
Cc:	David Miller <davem@...emloft.net>,
	Alasdair G Kergon <agk@...hat.com>,
	Mike Snitzer <snitzer@...hat.com>, Jens Axboe <axboe@...com>,
	dm-devel@...hat.com, Andrew Morton <akpm@...ux-foundation.org>,
	david.s.gordon@...el.com, Tom Lendacky <thomas.lendacky@....com>,
	Robert Jarzmik <robert.jarzmik@...e.fr>,
	Masahiro Yamada <yamada.masahiro@...ionext.com>,
	smueller@...onox.de, tadeusz.struk@...el.com,
	Masanari Iida <standby24x7@...il.com>, shli@...nel.org,
	Mark Brown <broonie@...nel.org>,
	Linus Walleij <linus.walleij@...aro.org>,
	Arnd Bergmann <arnd@...db.de>,
	LKML <linux-kernel@...r.kernel.org>,
	linux-crypto@...r.kernel.org, linux-raid@...r.kernel.org
Subject: Re: [PATCH v2 0/4] Introduce bulk mode for crypto engine framework

On 18 April 2016 at 16:04, Herbert Xu <herbert@...dor.apana.org.au> wrote:
> On Mon, Apr 18, 2016 at 03:58:59PM +0800, Baolin Wang wrote:
>>
>> That depends on the hardware engine. Some cipher hardware engines
>> (like xts(aes) engine) can handle the intermediate values (IV) by
>> themselves in one bulk block, which means we can increase the size of
>> the request by merging request rather than always 512 bytes and thus
>> increase the hardware engine processing speed. But for some other
>> hardware engines (like cbc(aes) engine), they can not support bulk
>> block, must sector by sector. So the engine drivers can select the
>> suitable mode to do encryption/decryption.
>
> So what is this supposed to handle, xts or cbc?

As I know, now cbc engine also need to handle requests sector by
sector, but for xts/ecb engine can support bulk block, which means can
merge requests.

>
>> > Even with batching we should be involving the user because only the
>> > user knows (if anyone does) whether more data will be forthcoming.
>>
>> If this cipher engine can support bulk block encryption, the crypto
>> engine framework can merge requests if they are eligible
>> automatically. Don't need to worry about how many data will be
>> forthcoming.
>
> Merging is simply wrong when the data is coming in as one piece
> and you've just artifically broken it up, only to merge it later.

It will not broke it up,  and it will check if the requests coming
from dm-crypt can be merged together.

>
> If the data can be merged then it should have stayed as one piece
> rather than being fragmented.

Yes, usually one whole block can be merged into one request as the latency.

>
> Cheers,
> --
> Email: Herbert Xu <herbert@...dor.apana.org.au>
> Home Page: http://gondor.apana.org.au/~herbert/
> PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt



-- 
Baolin.wang
Best Regards