linux-kernel - Re: [PATCHv3 10/10] x86/crypto: add pclmul acceleration for crc64

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Message-ID: <20220222171405.GA1782521@dhcp-10-100-145-180.wdc.com>
Date:   Tue, 22 Feb 2022 09:14:05 -0800
From:   Keith Busch <kbusch@...nel.org>
To:     David Laight <David.Laight@...lab.com>
Cc:     "linux-nvme@...ts.infradead.org" <linux-nvme@...ts.infradead.org>,
        "linux-block@...r.kernel.org" <linux-block@...r.kernel.org>,
        "linux-crypto@...r.kernel.org" <linux-crypto@...r.kernel.org>,
        "x86@...nel.org" <x86@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "axboe@...nel.dk" <axboe@...nel.dk>, "hch@....de" <hch@....de>,
        "martin.petersen@...cle.com" <martin.petersen@...cle.com>,
        "colyli@...e.de" <colyli@...e.de>
Subject: Re: [PATCHv3 10/10] x86/crypto: add pclmul acceleration for crc64

On Tue, Feb 22, 2022 at 05:02:16PM +0000, David Laight wrote:
> From: Keith Busch
> > Sent: 22 February 2022 16:32
> > 
> > The crc64 table lookup method is inefficient, using a significant number
> > of CPU cycles in the block stack per IO. If available on x86, use a
> > PCLMULQDQ implementation to accelerate the calculation.
> > 
> > The assembly from this patch was mostly generated by gcc from a C
> > program using library functions provided by x86 intrinsics, and measures
> > ~20x faster than the table lookup.
> 
> I think I'd like to see the C code and compiler options used to
> generate the assembler as comments in the committed source file.
> Either that or reasonable comments in the assembler.

The C code, compiled as "gcc -O3 -msse4 -mpclmul -S", was adapted from
this found on the internet:

  https://github.com/rawrunprotected/crc/blob/master/crc64.c

I just ported it to linux, changed the poly parameters and removed the
unnecessary stuff. 
 
I'm okay with dropping this patch from the series for now since I don't
think I'm qualified to write it. :) I just needed something to test the
crytpo module registration.