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From:   Ard Biesheuvel <ardb@kernel.org>
Date:   Wed, 29 Jul 2020 22:09:41 +0300
Message-ID: <CAMj1kXFK4xkieEpjW+ekYf9am6Ob15aGsnmWJMfn=LD_4oCuXg@mail.gmail.com>
Subject: Re: Help getting aesni crypto patch upstream
To:     Ben Greear <greearb@candelatech.com>
Cc:     Linux Crypto Mailing List <linux-crypto@vger.kernel.org>
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On Wed, 29 Jul 2020 at 15:27, Ben Greear <greearb@candelatech.com> wrote:
>
> On 7/28/20 11:06 PM, Ard Biesheuvel wrote:
> > On Wed, 29 Jul 2020 at 01:03, Ben Greear <greearb@candelatech.com> wrote:
> >>
> >> Hello,
> >>
> >> As part of my wifi test tool, I need to do decrypt AES on the CPU, and the only way this
> >> performs well is to use aesni.  I've been using a patch for years that does this, but
> >> recently somewhere between 5.4 and 5.7, the API I've been using has been removed.
> >>
> >> Would anyone be interested in getting this support upstream?  I'd be happy to pay for
> >> the effort.
> >>
> >> Here is the patch in question:
> >>
> >> https://github.com/greearb/linux-ct-5.7/blob/master/wip/0001-crypto-aesni-add-ccm-aes-algorithm-implementation.patch
> >>
> >> Please keep me in CC, I'm not subscribed to this list.
> >>
> >
> > Hi Ben,
> >
> > Recently, the x86 FPU handling was improved to remove the overhead of
> > preserving/restoring of the register state, so the issue that this
> > patch fixes may no longer exist. Did you try?
> >
> > In any case, according to the commit log on that patch, the problem is
> > in the MAC generation, so it might be better to add a cbcmac(aes)
> > implementation only, and not duplicate all the CCM boilerplate.
> >
>
> Hello,
>
> I don't know all of the details, and do not understand the crypto subsystem,
> but I am pretty sure that I need at least some of this patch.
>

Whether this is true is what I am trying to get clarified.

Your patch works around a performance bottleneck related to the use of
AES-NI instructions in the kernel, which has been addressed recently.
If the issue still exists, we can attempt to devise a fix for it,
which may or may not be based on this patch.

> If you can suggest a patch to try I'll be happy to test it to see how it
> performs.
>

Please share performance numbers of an old kernel with this patch
applied, and a recent one without. If that shows there is in fact an
issue, we will do something about it.

>
> --
> Ben Greear <greearb@candelatech.com>
> Candela Technologies Inc  http://www.candelatech.com