[PATCH v2] arm64: Implement optimised IP checksum helpers

[James Morse]

Hi Robin,

On 31/05/16 12:22, Robin Murphy wrote:
> AArch64 is capable of 128-bit memory accesses without alignment
> restrictions, which makes it both possible and highly practical to slurp
> up a typical 20-byte IP header in just 2 loads. Implement our own
> version of ip_fast_checksum() to take advantage of that, resulting in
> considerably fewer instructions and memory accesses than the generic
> version. We can also get more optimal code generation for csum_fold() by
> defining it a slightly different way round from the generic version, so
> throw that into the mix too.
> 
> Suggested-by: Luke Starrett <luke.starrett at broadcom.com>
> Acked-by: Luke Starrett <luke.starrett at broadcom.com>
> Signed-off-by: Robin Murphy <robin.murphy at arm.com>
> ---
> 
> Minor changes: include types.h for correctness, add Luke's ack.
> 
>  arch/arm64/include/asm/checksum.h | 51 +++++++++++++++++++++++++++++++++++++++

Maybe a nit, don't you need to remove the 'generic-y += checksum.h' line from
arch/arm64/include/asm/Kbuild to avoid the generated version being created too? [0]

The compiler on my box picks your header in preference to the generated one, but
[1] suggests it isn't to be trusted!


Thanks,

James

[0] d8ecc5cd8e22 ("kbuild: asm-generic support")
[1] https://lkml.org/lkml/2016/5/23/78