Re: [RFC v4 2/4] crypto: Introduce CRYPTO_ALG_BULK flag

Hi Herbert,

On 8 June 2016 at 10:00, Baolin Wang [off-list ref] wrote:

Hi Herbert,

On 7 June 2016 at 22:16, Herbert Xu [off-list ref] wrote:

quoted

On Tue, Jun 07, 2016 at 08:17:05PM +0800, Baolin Wang wrote:

quoted

Now some cipher hardware engines prefer to handle bulk block rather than one
sector (512 bytes) created by dm-crypt, cause these cipher engines can handle
the intermediate values (IV) by themselves in one bulk block. This 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.

So introduce 'CRYPTO_ALG_BULK' flag to indicate this cipher can support bulk
mode.

Signed-off-by: Baolin Wang <redacted>

Nack.  As I said before, please do it using explicit IV generators
like we do for IPsec.

OK. I would like to try your suggestion. Thanks.

After some investigation, I still think we should divide the bulk
request from dm-crypt into small request (each one is 512bytes) if
this algorithm is not support bulk mode (like CBC). We have talked
with dm-crypt
maintainers why dm-crypt always use 512 bytes as one request size in
below thread, could you please check it?
http://www.kernelhub.org/?p=2&msg=907022

That means if we move the IV handling into crypto API, we still can
not use bulk interface for all algorithm, for example we still need to
read/write with 512 bytes for CBC, you can't use 4k or more block on
CBC (and most other encryption modes). If only a part of 4k block is
written (and then system crash happens), CBC would corrupt the block
completely. It means if we map one whole bio with bulk interface in
dm-crypt, we need to divide into every 512 bytes requests in crypto
layer. So I don't think we can handle every algorithm with bulk
interface just moving the IV handling into crypto API. Thanks.

quoted

--
Email: Herbert Xu [off-list ref]
Home Page: http://gondor.apana.org.au/~herbert/
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--
Baolin.wang
Best Regards

-- 
Baolin.wang
Best Regards