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

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  Re: [RFC v4 2/4] crypto: Introduce CRYPTO_ALG_BULK flag Baolin Wang <baolin.wang@linaro.org> - 2016-06-15 08:30 +0200
    Re: [RFC v4 2/4] crypto: Introduce CRYPTO_ALG_BULK flag Herbert Xu <herbert@gondor.apana.org.au> - 2016-06-15 09:00 +0200
      Re: [RFC v4 2/4] crypto: Introduce CRYPTO_ALG_BULK flag Baolin Wang <baolin.wang@linaro.org> - 2016-06-15 09:40 +0200
        Re: [RFC v4 2/4] crypto: Introduce CRYPTO_ALG_BULK flag Herbert Xu <herbert@gondor.apana.org.au> - 2016-06-15 09:50 +0200
          Re: [RFC v4 2/4] crypto: Introduce CRYPTO_ALG_BULK flag Baolin Wang <baolin.wang@linaro.org> - 2016-06-15 10:50 +0200

#1422650 — Re: [RFC v4 2/4] crypto: Introduce CRYPTO_ALG_BULK flag

Hi Herbert,

On 8 June 2016 at 10:00, Baolin Wang <baolin.wang@linaro.org> wrote:
> Hi Herbert,
>
> On 7 June 2016 at 22:16, Herbert Xu <herbert@gondor.apana.org.au> wrote:
>> On Tue, Jun 07, 2016 at 08:17:05PM +0800, Baolin Wang wrote:
>>> 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 <baolin.wang@linaro.org>
>>
>> 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.

>
>> --
>> Email: Herbert Xu <herbert@gondor.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



-- 
Baolin.wang
Best Regards

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#1422673

On Wed, Jun 15, 2016 at 02:27:04PM +0800, Baolin Wang wrote:
> 
> 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 link only points to an email about an oops.

Diggin through that thread, the only objection I have seen is about
the fact that you have to generate a fresh IV for each sector, which
is precisely what I'm suggesting that you do.

IOW, implement the IV generators in the crypto API, and then you can
easily generate a new IV (if necessary) for each sector.

> 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.

Of course you would do CBC in 512-byte blocks, but my point is that
you should do this in a crypto API algorithm, rather than dm-crypt
as we do now.  Once you implement that then dm-crypt can treat
every algorithm as if they supported bulk processing.

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

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#1422714

On 15 June 2016 at 14:49, Herbert Xu <herbert@gondor.apana.org.au> wrote:
> On Wed, Jun 15, 2016 at 02:27:04PM +0800, Baolin Wang wrote:
>>
>> 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 link only points to an email about an oops.

Ah, sorry. Would you check this thread?
http://lkml.iu.edu/hypermail/linux/kernel/1601.1/03829.html

>
> Diggin through that thread, the only objection I have seen is about
> the fact that you have to generate a fresh IV for each sector, which
> is precisely what I'm suggesting that you do.
>
> IOW, implement the IV generators in the crypto API, and then you can
> easily generate a new IV (if necessary) for each sector.
>
>> 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.
>
> Of course you would do CBC in 512-byte blocks, but my point is that
> you should do this in a crypto API algorithm, rather than dm-crypt
> as we do now.  Once you implement that then dm-crypt can treat
> every algorithm as if they supported bulk processing.

But that means we should divide the bulk request into 512-byte size
requests and break up the mapped sg table for each request. Another
hand we should allocate memory for each request in crypto layer, which
dm-crypt have supplied one high efficiency way. I think these are
really top level how to use the crypro APIs, does that need to move
into crypto laryer? Thanks.

>
> Cheers,
> --
> Email: Herbert Xu <herbert@gondor.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

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#1422727

On Wed, Jun 15, 2016 at 03:38:02PM +0800, Baolin Wang wrote:
>
> But that means we should divide the bulk request into 512-byte size
> requests and break up the mapped sg table for each request. Another
> hand we should allocate memory for each request in crypto layer, which
> dm-crypt have supplied one high efficiency way. I think these are
> really top level how to use the crypro APIs, does that need to move
> into crypto laryer? Thanks.

I have already explained to you how you can piggy-back off dm-crypt's
allocation, so what's the problem?
-- 
Email: Herbert Xu <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt

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#1422791

On 15 June 2016 at 15:39, Herbert Xu <herbert@gondor.apana.org.au> wrote:
> On Wed, Jun 15, 2016 at 03:38:02PM +0800, Baolin Wang wrote:
>>
>> But that means we should divide the bulk request into 512-byte size
>> requests and break up the mapped sg table for each request. Another
>> hand we should allocate memory for each request in crypto layer, which
>> dm-crypt have supplied one high efficiency way. I think these are
>> really top level how to use the crypro APIs, does that need to move
>> into crypto laryer? Thanks.
>
> I have already explained to you how you can piggy-back off dm-crypt's
> allocation, so what's the problem?

Because the request created in dm-crypt is connecting with dm-crypt
closely, I am worried if it can work or introduce other issues if we
move these top level things into crypto layer. Anyway I will try to do
that. Thanks.

> --
> Email: Herbert Xu <herbert@gondor.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

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