Re: Crypto Update for 2.6.38

From: Linus Torvalds
Date: Thu Jan 06 2011 - 13:06:15 EST

On Wed, Jan 5, 2011 at 4:01 PM, Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxxx> wrote:
> * Crypto API interface for user-space (hash + skcipher)

Is there really any point to this? And can we get more explanation of
what the interface is, and who would use it?

If you need crypto in user space, it's almost invariably better done
in user space. If the CPU can do crypto on its own, and doesn't expose
those instructions to user space, it's just a stupid CPU - and the
user/kernel transfer is likely going to make it slower than a pure
software approach for any but the biggest transfers.

And if the crypto engine is off-chip, the sw version is going to be
faster anyway except for possible async versions that are hard to
interface to user space.

So I really need more convincing about the whole user-space interface.
Adding new interfaces willy-nilly isn't a good idea. They need damn
good reasons.

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