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

Keith Busch
2022-02-22T17:14:13Z

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.