From: Stephan Mueller <smueller@chronox.de>
To: Phil Sutter <phil@nwl.cc>
Cc: Hannes Frederic Sowa <hannes@stressinduktion.org>,
        Herbert Xu <herbert@gondor.apana.org.au>,
        Tom Herbert <tom@herbertland.com>, netdev@vger.kernel.org,
        davem@davemloft.net, Sowmini Varadhan <sowmini.varadhan@oracle.com>,
        linux-crypto@vger.kernel.org, linux-kernel@vger.kernel.org,
        kernel-team@fb.com
Subject: Re: [RFC PATCH 2/2] Crypto kernel tls socket
Date: Tue, 24 Nov 2015 13:36:34 +0100
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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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