netdev - Re: [RFC PATCH 2/2] Crypto kernel tls socket

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Date:	Tue, 24 Nov 2015 13:36:34 +0100
From:	Stephan Mueller <smueller@...onox.de>
To:	Phil Sutter <phil@....cc>
Cc:	Hannes Frederic Sowa <hannes@...essinduktion.org>,
	Herbert Xu <herbert@...dor.apana.org.au>,
	Tom Herbert <tom@...bertland.com>, netdev@...r.kernel.org,
	davem@...emloft.net,
	Sowmini Varadhan <sowmini.varadhan@...cle.com>,
	linux-crypto@...r.kernel.org, linux-kernel@...r.kernel.org,
	kernel-team@...com
Subject: Re: [RFC PATCH 2/2] Crypto kernel tls socket

Am Dienstag, 24. November 2015, 12:54:07 schrieb Phil Sutter:

Hi Phil,
>
>There "still" are dedicated crypto engines out there which need a driver
>to be accessed, so using them from userspace is not as simple as with
>padlock or AESNI. This was the reasoning behind the various cryptodev
>implementations and af_alg. Using those to establish a TLS connection
>with OpenSSL means to fetch encrypted data to userspace first and then
>feed it to the kernel again for decryption. Using cryptodev-linux, this
>will be zero-copy, but still there's an additional context switch
>involved which the approach here avoids.

Well, when being nasty, I could ask, why not putting the entire web server 
into the kernel. Heck, why not getting rid of user space?

Sorry, I could not resist. :-)

But back to the technical discussion. My main concern is that TLS is a big 
protocol and it is by far not the only crypto protocol where all those 
protocols seem to uses the same crypto primitives. And to me, there should be 
a good reason why software executes in supervisor state. Simply saving some 
context switches is not a good argument, because the context switches are 
there for a reason: to keep the system safe and secure.

Ciao
Stephan
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