linux-kernel - Re: Locking for HW crypto accelerators

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Date:   Thu, 30 Aug 2018 15:59:51 +0200
From:   Krzysztof Kozlowski <krzk@...nel.org>
To:     k.konieczny@...tner.samsung.com
Cc:     smueller@...onox.de, herbert@...dor.apana.org.au,
        davem@...emloft.net, linux-crypto@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: Locking for HW crypto accelerators

On Thu, 30 Aug 2018 at 15:27, Kamil Konieczny
<k.konieczny@...tner.samsung.com> wrote:
>
> On 30.08.2018 15:09, Krzysztof Kozlowski wrote:
> > [...]
> > Thanks Stephan for hints. Let's assume the each of init, update and
> > final are atomic... but how about the relation between update and
> > final? I have two concurrent users in user-space but only one HW:
> >
> > Process A:             Process B:
> > init() and set_key()
> >                        init() and different key
> > update(some_data)
> >                        update(different_data)
> > final()
> >                        final()
> >
> > The final() from process A will now produce the result of hashing/CRC
> > of some_data and different_data (and even maybe mixed with init() for
> > different key). All because in the meantime process B added its own
> > data to the HW.
> >
> > Best regards,
> > Krzysztof
> Can your hardware do export/import ?
>
> If yes, you can use workqueue and guard HW with spinlock,
> as in exynos hash in s5p-sss.c (or see other drivers).

Yes, workqueue doing all necessary HW initialization would be the
solution here as well. The point is what later Herbert wrote - I need
to take care about the HW state because the requests even for shash
will be coming in random order.

Best regards,
Krzysztof