Re: Question about ahash export and import

On Tue, Sep 26, 2017 at 12:36 PM, Christophe LEROY
[off-list ref] wrote:

Hello,

Today, the talitos driver dma maps/unmaps context and keys at every single
request.
I'm looking at doing the dma mapping at hash init and doing unmapping at
final/finup/digest

However, I'm wondering how to manage hash exports and imports. I was
initially thinking about doing a dma_sync_for_cpu() before any export and a
dma_sync_for_device() after any export, but that supposes that the dma area
is already mapped, which means that we have done the init and not yet done a
final/finup/digest.

I'm a bit sceptic when reading the following text in include/crypto/hash.h :

@export: Export partial state of the transformation. This function dumps the
 *          entire state of the ongoing transformation into a provided block
of
 *          data so it can be @import 'ed back later on. This is useful in
case
 *          you want to save partial result of the transformation after
 *          processing certain amount of data and reload this partial result
 *          multiple times later on for multiple re-use


Does it mean that import may be called in lieu of hash init, or is hash init
always called before doing an import ?

I believe import is called in lieu of init.

See the example is testmgr.c here:
http://elixir.free-electrons.com/linux/latest/source

import is called on a freshly allocated request (save for set_crypt
and set_callback), followed by
a call to update.

Gilad

Thanks
Christophe

-- 
Gilad Ben-Yossef
Chief Coffee Drinker

"If you take a class in large-scale robotics, can you end up in a
situation where the homework eats your dog?"
 -- Jean-Baptiste Queru