linux-kernel - RE: [PATCH V8 1/5] crypto: Multi-buffer encryption infrastructure support

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Date:   Thu, 19 Apr 2018 00:54:16 +0000
From:   "Dey, Megha" <megha.dey@...el.com>
To:     Herbert Xu <herbert@...dor.apana.org.au>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-crypto@...r.kernel.org" <linux-crypto@...r.kernel.org>,
        "davem@...emloft.net" <davem@...emloft.net>
Subject: RE: [PATCH V8 1/5] crypto: Multi-buffer encryption infrastructure
 support



>-----Original Message-----
>From: Herbert Xu [mailto:herbert@...dor.apana.org.au]
>Sent: Wednesday, April 18, 2018 4:01 AM
>To: Dey, Megha <megha.dey@...el.com>
>Cc: linux-kernel@...r.kernel.org; linux-crypto@...r.kernel.org;
>davem@...emloft.net
>Subject: Re: [PATCH V8 1/5] crypto: Multi-buffer encryption infrastructure
>support
>
>On Tue, Apr 17, 2018 at 06:40:17PM +0000, Dey, Megha wrote:
>>
>>
>> >-----Original Message-----
>> >From: Herbert Xu [mailto:herbert@...dor.apana.org.au]
>> >Sent: Friday, March 16, 2018 7:54 AM
>> >To: Dey, Megha <megha.dey@...el.com>
>> >Cc: linux-kernel@...r.kernel.org; linux-crypto@...r.kernel.org;
>> >davem@...emloft.net
>> >Subject: Re: [PATCH V8 1/5] crypto: Multi-buffer encryption
>> >infrastructure support
>> >
>> >I have taken a deeper look and I'm even more convinced now that
>> >mcryptd is simply not needed in your current model.
>> >
>> >The only reason you would need mcryptd is if you need to limit the
>> >rate of requests going into the underlying mb algorithm.
>> >
>> >However, it doesn't do that all.  Even though it seems to have a
>> >batch size of 10, but because it immediately reschedules itself after
>> >the batch runs out, it's essentially just dumping all requests at the
>> >underlying algorithm as fast as they're coming in.  The underlying
>> >algorithm doesn't have need throttling anyway because it'll do the work
>when the queue is full synchronously.
>> >
>> >So why not just get rid of mcryptd completely and expose the
>> >underlying algorithm as a proper async skcipher/hash?
>>
>> Hi Herbert,
>>
>> Most part of the cryptd.c and mcryptd.c are similar, except the logic
>> used to flush out partially completed jobs in the case of multibuffer
>algorithms.
>>
>> I think I will try to merge the cryptd and mcryptd adding necessary quirks for
>multibuffer where needed.
>
>I think you didn't quite get my point.  From what I'm seeing you don't need
>either cryptd or mcryptd.  You just need to expose the underlying mb
>algorithm directly.

Hi Herbert,

Yeah I think I misunderstood. I think what you mean is to remove mcryptd.c completely and avoid the extra layer of indirection to call the underlying algorithm, instead call it directly, correct?

So currently we have 3 algorithms registered for every multibuffer algorithm:
name         : __sha1-mb
driver       : mcryptd(__intel_sha1-mb)

name         : sha1
driver       : sha1_mb

name         : __sha1-mb
driver       : __intel_sha1-mb

If we remove mcryptd, then we will have just the 2?

The outer algorithm:sha1-mb, will 
>
>So I'm not sure what we would gain from merging cryptd and mcryptd.
>
>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