linux-kernel - Re: [PATCH 3/4] crypto: [sha] glue code for Intel SHA extensions optimized SHA1 & SHA256

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Date:	Fri, 11 Sep 2015 19:02:04 +0200
From:	Stephan Mueller <smueller@...onox.de>
To:	Tim Chen <tim.c.chen@...ux.intel.com>
Cc:	Herbert Xu <herbert@...dor.apana.org.au>,
	"H. Peter Anvin" <hpa@...or.com>,
	"David S.Miller" <davem@...emloft.net>,
	Sean Gulley <sean.m.gulley@...el.com>,
	Chandramouli Narayanan <mouli_7982@...oo.com>,
	Vinodh Gopal <vinodh.gopal@...el.com>,
	James Guilford <james.guilford@...el.com>,
	Wajdi Feghali <wajdi.k.feghali@...el.com>,
	Jussi Kivilinna <jussi.kivilinna@....fi>,
	linux-crypto@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/4] crypto: [sha] glue code for Intel SHA extensions optimized SHA1 & SHA256

Am Donnerstag, 10. September 2015, 17:04:31 schrieb Tim Chen:

Hi Tim,
>
>Is there a scenario you can think of
>when a lower performing sha1 transform needs to
>be exposed as a separate driver?

My immediate concern is testing: it is hard to test the individual 
implementations.
>
>Otherwise the glue code logic will only expose the
>best performing one for a cpu and hide the others, which was intentional
>on our part to prevent a lower performing sha from getting used.

Agreed, but the kernel crypto API does that already using the priorities -- 
IMHO a very clean and easy to interpret solution.

Furthermore, if somebody really has a need to not use the fastest HW 
implementation, the kernel crypto API allows him to do that. With the hard-
wired approach in the glue file, you are stuck.


Ciao
Stephan
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