linux-kernel - Re: [CRYPTO] is it really optimized ?

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Message-ID: <ada7isb3qr2.fsf@cisco.com>
Date:	Tue, 17 Apr 2007 09:33:21 -0700
From:	Roland Dreier <rdreier@...co.com>
To:	"Francis Moreau" <francis.moro@...il.com>
Cc:	"Herbert Xu" <herbert@...dor.apana.org.au>,
	helge.hafting@...el.hist.no, linux-kernel@...r.kernel.org,
	linux-crypto@...r.kernel.org
Subject: Re: [CRYPTO] is it really optimized ?

 > > I wonder if there's some way you can cache the last caller and reload
 > > the key lazily (only when it changes).
 > 
 > yes something that allows crypto drivers to detect if the key has
 > changed would be good.

It seems trivial to keep the last key you were given and do a quick
memcmp in your setkey method to see if it's different from the last
key you pushed to hardware, and set a flag if it is.  Then only do
your set_key() if you have a new key to pass to hardware.

I'm assuming the expense is in the aes_write() calls, and you could
avoid them if you know you're not writing something new.

 - R.
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