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From:   Ard Biesheuvel <ard.biesheuvel@linaro.org>
Date:   Fri, 4 Oct 2019 16:38:51 +0200
Message-ID: <CAKv+Gu8cuMcjqfDyzcShxd8cimjhKrBELjNoJ5xKgWmSzZ4S5g@mail.gmail.com>
Subject: Re: [PATCH v2 05/20] crypto: mips/chacha - import accelerated 32r2
 code from Zinc
To:     "Jason A. Donenfeld" <Jason@zx2c4.com>
Cc:     "open list:HARDWARE RANDOM NUMBER GENERATOR CORE" 
        <linux-crypto@vger.kernel.org>,
        Herbert Xu <herbert@gondor.apana.org.au>,
        David Miller <davem@davemloft.net>,
        Greg KH <gregkh@linuxfoundation.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Samuel Neves <sneves@dei.uc.pt>,
        Dan Carpenter <dan.carpenter@oracle.com>,
        Arnd Bergmann <arnd@arndb.de>,
        Eric Biggers <ebiggers@google.com>,
        Andy Lutomirski <luto@kernel.org>,
        Will Deacon <will@kernel.org>, Marc Zyngier <maz@kernel.org>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Martin Willi <martin@strongswan.org>,
        Peter Zijlstra <peterz@infradead.org>,
        Josh Poimboeuf <jpoimboe@redhat.com>,
        =?UTF-8?Q?Ren=C3=A9_van_Dorst?= <opensource@vdorst.com>
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On Fri, 4 Oct 2019 at 16:38, Ard Biesheuvel <ard.biesheuvel@linaro.org> wro=
te:
>
> On Fri, 4 Oct 2019 at 15:46, Jason A. Donenfeld <Jason@zx2c4.com> wrote:
> >
> > On Wed, Oct 02, 2019 at 04:16:58PM +0200, Ard Biesheuvel wrote:
> > > This integrates the accelerated MIPS 32r2 implementation of ChaCha
> > > into both the API and library interfaces of the kernel crypto stack.
> > >
> > > The significance of this is that, in addition to becoming available
> > > as an accelerated library implementation, it can also be used by
> > > existing crypto API code such as Adiantum (for block encryption on
> > > ultra low performance cores) or IPsec using chacha20poly1305. These
> > > are use cases that have already opted into using the abstract crypto
> > > API. In order to support Adiantum, the core assembler routine has
> > > been adapted to take the round count as a function argument rather
> > > than hardcoding it to 20.
> >
> > Could you resubmit this with first my original commit and then with you=
r
> > changes on top? I'd like to see and be able to review exactly what's
> > changed. If I recall correctly, Ren=C3=A9 and I were really starved for
> > registers and tried pretty hard to avoid spilling to the stack, so I'm
> > interested to learn how you crammed a bit more sauce in there.
> >
>
> The round count is passed via the fifth function parameter, so it is
> already on the stack. Reloading it for every block doesn't sound like
> a huge deal to me.
>
> > I also wonder if maybe it'd be better to just leave this as is with 20
> > rounds, which it was previously optimized for, and just not do
> > accelerated Adiantum for MIPS. Android has long since given up on the
> > ISA entirely.
>
> Adiantum does not depend on Android - anyone running linux on his MIPS
> router can use it if they want encrypted storage.

But to answer your first question: sure, i will split off the changes.